diff --git a/blockchain/pool_test.go b/blockchain/pool_test.go
index 8e6dbee9..220bc5ce 100644
--- a/blockchain/pool_test.go
+++ b/blockchain/pool_test.go
@@ -35,6 +35,7 @@ func TestBasic(t *testing.T) {
 	requestsCh := make(chan BlockRequest, 100)
 	pool := NewBlockPool(start, requestsCh, timeoutsCh)
 	pool.Start()
+	defer pool.Stop()
 
 	// Introduce each peer.
 	go func() {
@@ -76,8 +77,6 @@ func TestBasic(t *testing.T) {
 			}()
 		}
 	}
-
-	pool.Stop()
 }
 
 func TestTimeout(t *testing.T) {
@@ -87,6 +86,7 @@ func TestTimeout(t *testing.T) {
 	requestsCh := make(chan BlockRequest, 100)
 	pool := NewBlockPool(start, requestsCh, timeoutsCh)
 	pool.Start()
+	defer pool.Stop()
 
 	for _, peer := range peers {
 		log.Info("Peer", "id", peer.id)
@@ -131,6 +131,4 @@ func TestTimeout(t *testing.T) {
 			log.Info("TEST: Pulled new BlockRequest", "request", request)
 		}
 	}
-
-	pool.Stop()
 }
diff --git a/consensus/state.go b/consensus/state.go
index 63616cbd..d6943581 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -283,7 +283,7 @@ func NewConsensusState(config cfg.Config, state *sm.State, proxyAppConn proxy.Ap
 //----------------------------------------
 // Public interface
 
-// implements events.Eventable
+// SetEventSwitch implements events.Eventable
 func (cs *ConsensusState) SetEventSwitch(evsw types.EventSwitch) {
 	cs.evsw = evsw
 }
diff --git a/glide.lock b/glide.lock
index e7988802..71b549db 100644
--- a/glide.lock
+++ b/glide.lock
@@ -164,4 +164,12 @@ imports:
   - stats
   - tap
   - transport
-testImports: []
+testImports:
+- name: github.com/davecgh/go-spew
+  version: 6d212800a42e8ab5c146b8ace3490ee17e5225f9
+  subpackages:
+  - spew
+- name: github.com/pmezard/go-difflib
+  version: d8ed2627bdf02c080bf22230dbb337003b7aba2d
+  subpackages:
+  - difflib
diff --git a/node/node.go b/node/node.go
index 6815c779..7a88f2d0 100644
--- a/node/node.go
+++ b/node/node.go
@@ -82,7 +82,7 @@ func NewNode(config cfg.Config, privValidator *types.PrivValidator, clientCreato
 	}
 
 	// reload the state (it may have been updated by the handshake)
-	state = sm.LoadState(stateDB)
+	state = sm.GetState(config, stateDB)
 
 	// Generate node PrivKey
 	privKey := crypto.GenPrivKeyEd25519()
diff --git a/state/execution.go b/state/execution.go
index aa911301..0a82c6da 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -2,26 +2,26 @@ package state
 
 import (
 	"errors"
+	"fmt"
 
-	"github.com/ebuchman/fail-test"
-
+	fail "github.com/ebuchman/fail-test"
 	abci "github.com/tendermint/abci/types"
 	. "github.com/tendermint/go-common"
-	"github.com/tendermint/go-crypto"
+	crypto "github.com/tendermint/go-crypto"
 	"github.com/tendermint/tendermint/proxy"
+	txindexer "github.com/tendermint/tendermint/state/tx/indexer"
 	"github.com/tendermint/tendermint/types"
 )
 
-//--------------------------------------------------
-// Execute the block
-
-// Execute the block to mutate State.
-// Validates block and then executes Data.Txs in the block.
-func (s *State) ExecBlock(eventCache types.Fireable, proxyAppConn proxy.AppConnConsensus, block *types.Block, blockPartsHeader types.PartSetHeader) error {
-
+// ExecBlock executes the block to mutate State.
+// + validates the block
+// + executes block.Txs on the proxyAppConn
+// + updates validator sets
+// + returns block.Txs results
+func (s *State) ExecBlock(eventCache types.Fireable, proxyAppConn proxy.AppConnConsensus, block *types.Block, blockPartsHeader types.PartSetHeader) ([]*types.TxResult, error) {
 	// Validate the block.
 	if err := s.validateBlock(block); err != nil {
-		return ErrInvalidBlock(err)
+		return nil, ErrInvalidBlock(err)
 	}
 
 	// compute bitarray of validators that signed
@@ -33,11 +33,11 @@ func (s *State) ExecBlock(eventCache types.Fireable, proxyAppConn proxy.AppConnC
 	nextValSet := valSet.Copy()
 
 	// Execute the block txs
-	changedValidators, err := execBlockOnProxyApp(eventCache, proxyAppConn, block)
+	txResults, changedValidators, err := execBlockOnProxyApp(eventCache, proxyAppConn, block)
 	if err != nil {
 		// There was some error in proxyApp
 		// TODO Report error and wait for proxyApp to be available.
-		return ErrProxyAppConn(err)
+		return nil, ErrProxyAppConn(err)
 	}
 
 	// update the validator set
@@ -54,16 +54,22 @@ func (s *State) ExecBlock(eventCache types.Fireable, proxyAppConn proxy.AppConnC
 
 	fail.Fail() // XXX
 
-	return nil
+	return txResults, nil
 }
 
 // Executes block's transactions on proxyAppConn.
-// Returns a list of updates to the validator set
+// Returns a list of transaction results and updates to the validator set
 // TODO: Generate a bitmap or otherwise store tx validity in state.
-func execBlockOnProxyApp(eventCache types.Fireable, proxyAppConn proxy.AppConnConsensus, block *types.Block) ([]*abci.Validator, error) {
-
+func execBlockOnProxyApp(eventCache types.Fireable, proxyAppConn proxy.AppConnConsensus, block *types.Block) ([]*types.TxResult, []*abci.Validator, error) {
 	var validTxs, invalidTxs = 0, 0
 
+	txResults := make([]*types.TxResult, len(block.Txs))
+
+	txHashToIndexMap := make(map[string]int)
+	for index, tx := range block.Txs {
+		txHashToIndexMap[string(tx.Hash())] = index
+	}
+
 	// Execute transactions and get hash
 	proxyCb := func(req *abci.Request, res *abci.Response) {
 		switch r := res.Value.(type) {
@@ -73,21 +79,28 @@ func execBlockOnProxyApp(eventCache types.Fireable, proxyAppConn proxy.AppConnCo
 			// Blocks may include invalid txs.
 			// reqDeliverTx := req.(abci.RequestDeliverTx)
 			txError := ""
-			apTx := r.DeliverTx
-			if apTx.Code == abci.CodeType_OK {
-				validTxs += 1
+			txResult := r.DeliverTx
+			if txResult.Code == abci.CodeType_OK {
+				validTxs++
 			} else {
-				log.Debug("Invalid tx", "code", r.DeliverTx.Code, "log", r.DeliverTx.Log)
-				invalidTxs += 1
-				txError = apTx.Code.String()
+				log.Debug("Invalid tx", "code", txResult.Code, "log", txResult.Log)
+				invalidTxs++
+				txError = txResult.Code.String()
 			}
+
+			tx := types.Tx(req.GetDeliverTx().Tx)
+			index, ok := txHashToIndexMap[string(tx.Hash())]
+			if ok {
+				txResults[index] = &types.TxResult{uint64(block.Height), uint32(index), *txResult}
+			}
+
 			// NOTE: if we count we can access the tx from the block instead of
 			// pulling it from the req
 			event := types.EventDataTx{
-				Tx:    req.GetDeliverTx().Tx,
-				Data:  apTx.Data,
-				Code:  apTx.Code,
-				Log:   apTx.Log,
+				Tx:    tx,
+				Data:  txResult.Data,
+				Code:  txResult.Code,
+				Log:   txResult.Log,
 				Error: txError,
 			}
 			types.FireEventTx(eventCache, event)
@@ -99,7 +112,7 @@ func execBlockOnProxyApp(eventCache types.Fireable, proxyAppConn proxy.AppConnCo
 	err := proxyAppConn.BeginBlockSync(block.Hash(), types.TM2PB.Header(block.Header))
 	if err != nil {
 		log.Warn("Error in proxyAppConn.BeginBlock", "error", err)
-		return nil, err
+		return nil, nil, err
 	}
 
 	fail.Fail() // XXX
@@ -109,7 +122,7 @@ func execBlockOnProxyApp(eventCache types.Fireable, proxyAppConn proxy.AppConnCo
 		fail.FailRand(len(block.Txs)) // XXX
 		proxyAppConn.DeliverTxAsync(tx)
 		if err := proxyAppConn.Error(); err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 	}
 
@@ -119,7 +132,7 @@ func execBlockOnProxyApp(eventCache types.Fireable, proxyAppConn proxy.AppConnCo
 	respEndBlock, err := proxyAppConn.EndBlockSync(uint64(block.Height))
 	if err != nil {
 		log.Warn("Error in proxyAppConn.EndBlock", "error", err)
-		return nil, err
+		return nil, nil, err
 	}
 
 	fail.Fail() // XXX
@@ -128,7 +141,7 @@ func execBlockOnProxyApp(eventCache types.Fireable, proxyAppConn proxy.AppConnCo
 	if len(respEndBlock.Diffs) > 0 {
 		log.Info("Update to validator set", "updates", abci.ValidatorsString(respEndBlock.Diffs))
 	}
-	return respEndBlock.Diffs, nil
+	return txResults, respEndBlock.Diffs, nil
 }
 
 func updateValidators(validators *types.ValidatorSet, changedValidators []*abci.Validator) error {
@@ -218,26 +231,31 @@ func (s *State) validateBlock(block *types.Block) error {
 	return nil
 }
 
-//-----------------------------------------------------------------------------
-// ApplyBlock executes the block, then commits and updates the mempool atomically
-
-// Execute and commit block against app, save block and state
+// ApplyBlock executes the block, then commits and updates the mempool
+// atomically, optionally indexing transaction results.
 func (s *State) ApplyBlock(eventCache types.Fireable, proxyAppConn proxy.AppConnConsensus,
 	block *types.Block, partsHeader types.PartSetHeader, mempool types.Mempool) error {
 
-	// Run the block on the State:
-	// + update validator sets
-	// + run txs on the proxyAppConn
-	err := s.ExecBlock(eventCache, proxyAppConn, block, partsHeader)
+	txResults, err := s.ExecBlock(eventCache, proxyAppConn, block, partsHeader)
 	if err != nil {
-		return errors.New(Fmt("Exec failed for application: %v", err))
+		return fmt.Errorf("Exec failed for application: %v", err)
 	}
 
 	// lock mempool, commit state, update mempoool
 	err = s.CommitStateUpdateMempool(proxyAppConn, block, mempool)
 	if err != nil {
-		return errors.New(Fmt("Commit failed for application: %v", err))
+		return fmt.Errorf("Commit failed for application: %v", err)
 	}
+
+	batch := txindexer.NewBatch()
+	for i, r := range txResults {
+		if r != nil {
+			tx := block.Txs[i]
+			batch.Index(string(tx.Hash()), *r)
+		}
+	}
+	s.TxIndexer.Batch(batch)
+
 	return nil
 }
 
@@ -272,7 +290,7 @@ func (s *State) CommitStateUpdateMempool(proxyAppConn proxy.AppConnConsensus, bl
 // Returns the application root hash (result of abci.Commit)
 func ApplyBlock(appConnConsensus proxy.AppConnConsensus, block *types.Block) ([]byte, error) {
 	var eventCache types.Fireable // nil
-	_, err := execBlockOnProxyApp(eventCache, appConnConsensus, block)
+	_, _, err := execBlockOnProxyApp(eventCache, appConnConsensus, block)
 	if err != nil {
 		log.Warn("Error executing block on proxy app", "height", block.Height, "err", err)
 		return nil, err
diff --git a/state/state.go b/state/state.go
index c4c6d748..892c3874 100644
--- a/state/state.go
+++ b/state/state.go
@@ -10,6 +10,8 @@ import (
 	cfg "github.com/tendermint/go-config"
 	dbm "github.com/tendermint/go-db"
 	"github.com/tendermint/go-wire"
+	"github.com/tendermint/tendermint/state/tx"
+	txindexer "github.com/tendermint/tendermint/state/tx/indexer"
 	"github.com/tendermint/tendermint/types"
 )
 
@@ -38,6 +40,8 @@ type State struct {
 
 	// AppHash is updated after Commit
 	AppHash []byte
+
+	TxIndexer tx.Indexer `json:"-"` // Transaction indexer.
 }
 
 func LoadState(db dbm.DB) *State {
@@ -72,6 +76,7 @@ func (s *State) Copy() *State {
 		Validators:      s.Validators.Copy(),
 		LastValidators:  s.LastValidators.Copy(),
 		AppHash:         s.AppHash,
+		TxIndexer:       s.TxIndexer, // pointer here, not value
 	}
 }
 
@@ -125,12 +130,20 @@ func GetState(config cfg.Config, stateDB dbm.DB) *State {
 		state = MakeGenesisStateFromFile(stateDB, config.GetString("genesis_file"))
 		state.Save()
 	}
+
+	// Transaction indexing
+	store := dbm.NewDB("tx_indexer", config.GetString("db_backend"), config.GetString("db_dir"))
+	state.TxIndexer = txindexer.NewKV(store)
+
 	return state
 }
 
 //-----------------------------------------------------------------------------
 // Genesis
 
+// MakeGenesisStateFromFile reads and unmarshals state from the given file.
+//
+// Used during replay and in tests.
 func MakeGenesisStateFromFile(db dbm.DB, genDocFile string) *State {
 	genDocJSON, err := ioutil.ReadFile(genDocFile)
 	if err != nil {
@@ -143,6 +156,9 @@ func MakeGenesisStateFromFile(db dbm.DB, genDocFile string) *State {
 	return MakeGenesisState(db, genDoc)
 }
 
+// MakeGenesisState creates state from types.GenesisDoc.
+//
+// Used in tests.
 func MakeGenesisState(db dbm.DB, genDoc *types.GenesisDoc) *State {
 	if len(genDoc.Validators) == 0 {
 		Exit(Fmt("The genesis file has no validators"))
@@ -176,5 +192,6 @@ func MakeGenesisState(db dbm.DB, genDoc *types.GenesisDoc) *State {
 		Validators:      types.NewValidatorSet(validators),
 		LastValidators:  types.NewValidatorSet(nil),
 		AppHash:         genDoc.AppHash,
+		TxIndexer:       &txindexer.Null{}, // we do not need indexer during replay and in tests
 	}
 }
diff --git a/state/tx/indexer.go b/state/tx/indexer.go
new file mode 100644
index 00000000..759f141a
--- /dev/null
+++ b/state/tx/indexer.go
@@ -0,0 +1,21 @@
+package tx
+
+import (
+	txindexer "github.com/tendermint/tendermint/state/tx/indexer"
+	"github.com/tendermint/tendermint/types"
+)
+
+// Indexer interface defines methods to index and search transactions.
+type Indexer interface {
+
+	// Batch analyzes, indexes or stores a batch of transactions.
+	//
+	// NOTE We do not specify Index method for analyzing a single transaction
+	// here because it bears heavy perfomance loses. Almost all advanced indexers
+	// support batching.
+	Batch(b *txindexer.Batch) error
+
+	// Tx returns specified transaction or nil if the transaction is not indexed
+	// or stored.
+	Tx(hash string) (*types.TxResult, error)
+}
diff --git a/state/tx/indexer/batch.go b/state/tx/indexer/batch.go
new file mode 100644
index 00000000..3c64c886
--- /dev/null
+++ b/state/tx/indexer/batch.go
@@ -0,0 +1,32 @@
+package indexer
+
+import "github.com/tendermint/tendermint/types"
+
+// A Batch groups together multiple Index operations you would like performed
+// at the same time. The Batch structure is NOT thread-safe. You should only
+// perform operations on a batch from a single thread at a time. Once batch
+// execution has started, you may not modify it.
+type Batch struct {
+	Ops map[string]types.TxResult
+}
+
+// NewBatch creates a new Batch.
+func NewBatch() *Batch {
+	return &Batch{
+		Ops: make(map[string]types.TxResult),
+	}
+}
+
+// Index adds or updates entry for the given hash.
+func (b *Batch) Index(hash string, result types.TxResult) error {
+	if hash == "" {
+		return ErrorEmptyHash
+	}
+	b.Ops[hash] = result
+	return nil
+}
+
+// Size returns the total number of operations inside the batch.
+func (b *Batch) Size() int {
+	return len(b.Ops)
+}
diff --git a/state/tx/indexer/error.go b/state/tx/indexer/error.go
new file mode 100644
index 00000000..9d20593d
--- /dev/null
+++ b/state/tx/indexer/error.go
@@ -0,0 +1,6 @@
+package indexer
+
+import "errors"
+
+// ErrorEmptyHash indicates empty hash
+var ErrorEmptyHash = errors.New("Transaction hash cannot be empty")
diff --git a/state/tx/indexer/kv.go b/state/tx/indexer/kv.go
new file mode 100644
index 00000000..0c86d0a3
--- /dev/null
+++ b/state/tx/indexer/kv.go
@@ -0,0 +1,55 @@
+package indexer
+
+import (
+	"bytes"
+	"fmt"
+
+	db "github.com/tendermint/go-db"
+	"github.com/tendermint/go-wire"
+	"github.com/tendermint/tendermint/types"
+)
+
+// KV is a simplest possible indexer, backed by Key-Value storage (levelDB).
+// It could only index transaction by its identifier.
+type KV struct {
+	store db.DB
+}
+
+// NewKV returns new instance of KV indexer.
+func NewKV(store db.DB) *KV {
+	return &KV{store: store}
+}
+
+// Tx gets transaction from the KV storage and returns it or nil if the
+// transaction is not found.
+func (indexer *KV) Tx(hash string) (*types.TxResult, error) {
+	if hash == "" {
+		return nil, ErrorEmptyHash
+	}
+
+	rawBytes := indexer.store.Get([]byte(hash))
+	if rawBytes == nil {
+		return nil, nil
+	}
+
+	r := bytes.NewReader(rawBytes)
+	var n int
+	var err error
+	txResult := wire.ReadBinary(&types.TxResult{}, r, 0, &n, &err).(*types.TxResult)
+	if err != nil {
+		return nil, fmt.Errorf("Error reading TxResult: %v", err)
+	}
+
+	return txResult, nil
+}
+
+// Batch writes a batch of transactions into the KV storage.
+func (indexer *KV) Batch(b *Batch) error {
+	storeBatch := indexer.store.NewBatch()
+	for hash, result := range b.Ops {
+		rawBytes := wire.BinaryBytes(&result)
+		storeBatch.Set([]byte(hash), rawBytes)
+	}
+	storeBatch.Write()
+	return nil
+}
diff --git a/state/tx/indexer/kv_test.go b/state/tx/indexer/kv_test.go
new file mode 100644
index 00000000..0e3b0a7d
--- /dev/null
+++ b/state/tx/indexer/kv_test.go
@@ -0,0 +1,61 @@
+package indexer
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	abci "github.com/tendermint/abci/types"
+	db "github.com/tendermint/go-db"
+	"github.com/tendermint/tendermint/types"
+)
+
+func TestKVIndex(t *testing.T) {
+	indexer := &KV{store: db.NewMemDB()}
+
+	tx := types.Tx("HELLO WORLD")
+	txResult := &types.TxResult{1, 1, abci.ResponseDeliverTx{Data: []byte{0}, Code: abci.CodeType_OK, Log: ""}}
+	hash := string(tx.Hash())
+
+	batch := NewBatch()
+	batch.Index(hash, *txResult)
+	err := indexer.Batch(batch)
+	require.Nil(t, err)
+
+	loadedTxResult, err := indexer.Tx(hash)
+	require.Nil(t, err)
+	assert.Equal(t, txResult, loadedTxResult)
+}
+
+func benchmarkKVIndex(txsCount int, b *testing.B) {
+	txResult := &types.TxResult{1, 1, abci.ResponseDeliverTx{Data: []byte{0}, Code: abci.CodeType_OK, Log: ""}}
+
+	dir, err := ioutil.TempDir("", "tx_indexer_db")
+	if err != nil {
+		b.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	store := db.NewDB("tx_indexer", "leveldb", dir)
+	indexer := &KV{store: store}
+
+	batch := NewBatch()
+	for i := 0; i < txsCount; i++ {
+		batch.Index(fmt.Sprintf("hash%v", i), *txResult)
+	}
+
+	b.ResetTimer()
+
+	for n := 0; n < b.N; n++ {
+		err = indexer.Batch(batch)
+	}
+}
+
+func BenchmarkKVIndex1(b *testing.B)     { benchmarkKVIndex(1, b) }
+func BenchmarkKVIndex500(b *testing.B)   { benchmarkKVIndex(500, b) }
+func BenchmarkKVIndex1000(b *testing.B)  { benchmarkKVIndex(1000, b) }
+func BenchmarkKVIndex2000(b *testing.B)  { benchmarkKVIndex(2000, b) }
+func BenchmarkKVIndex10000(b *testing.B) { benchmarkKVIndex(10000, b) }
diff --git a/state/tx/indexer/null.go b/state/tx/indexer/null.go
new file mode 100644
index 00000000..b196a705
--- /dev/null
+++ b/state/tx/indexer/null.go
@@ -0,0 +1,16 @@
+package indexer
+
+import "github.com/tendermint/tendermint/types"
+
+// Null acts as a /dev/null.
+type Null struct{}
+
+// Tx panics.
+func (indexer *Null) Tx(hash string) (*types.TxResult, error) {
+	panic("You are trying to get the transaction from a null indexer")
+}
+
+// Batch returns nil.
+func (indexer *Null) Batch(batch *Batch) error {
+	return nil
+}
diff --git a/types/tx_result.go b/types/tx_result.go
new file mode 100644
index 00000000..c3ec0030
--- /dev/null
+++ b/types/tx_result.go
@@ -0,0 +1,14 @@
+package types
+
+import (
+	abci "github.com/tendermint/abci/types"
+)
+
+// TxResult contains results of executing the transaction.
+//
+// One usage is indexing transaction results.
+type TxResult struct {
+	Height            uint64
+	Index             uint32
+	DeliverTxResponse abci.ResponseDeliverTx
+}