diff --git a/src/interpreter/module.rs b/src/interpreter/module.rs
index e92c637..f5ecfbf 100644
--- a/src/interpreter/module.rs
+++ b/src/interpreter/module.rs
@@ -20,9 +20,12 @@ const DEFAULT_FRAME_STACK_LIMIT: usize = 1024;
 
 /// Execution context.
 #[derive(Clone)]
-pub struct ExecutionParams {
+pub struct ExecutionParams<St: 'static> {
 	/// Arguments.
 	pub args: Vec<RuntimeValue>,
+
+	/// State that can be used by host functions,
+	pub state: St,
 }
 
 /// Export type.
@@ -76,7 +79,7 @@ pub struct InternalFunction<'a> {
 	pub labels: &'a HashMap<usize, usize>,
 }
 
-impl ExecutionParams {
+impl<St> ExecutionParams<St> {
 	/// Add argument.
 	pub fn add_argument(mut self, arg: RuntimeValue) -> Self {
 		self.args.push(arg);
@@ -84,18 +87,20 @@ impl ExecutionParams {
 	}
 }
 
-impl Default for ExecutionParams {
+impl<St: Default> Default for ExecutionParams<St> {
 	fn default() -> Self {
 		ExecutionParams {
 			args: Vec::default(),
+			state: St::default(),
 		}
 	}
 }
 
-impl<'a> From<Vec<RuntimeValue>> for ExecutionParams {
-	fn from(args: Vec<RuntimeValue>) -> ExecutionParams {
+impl<'a, St: Default> From<Vec<RuntimeValue>> for ExecutionParams<St> {
+	fn from(args: Vec<RuntimeValue>) -> ExecutionParams<St> {
 		ExecutionParams {
-			args: args
+			args: args,
+			state: St::default(),
 		}
 	}
 }
diff --git a/src/interpreter/program.rs b/src/interpreter/program.rs
index 365a139..153c757 100644
--- a/src/interpreter/program.rs
+++ b/src/interpreter/program.rs
@@ -22,11 +22,11 @@ impl ProgramInstance {
 	}
 
 	/// Instantiate module with validation.
-	pub fn add_module<'a>(
+	pub fn add_module<'a, St: 'static>(
 		&mut self,
 		name: &str,
 		module: Module,
-		start_exec_params: ExecutionParams,
+		start_exec_params: ExecutionParams<St>,
 	) -> Result<ModuleId, Error> {
 		let mut extern_vals = Vec::new();
 		for import_entry in module.import_section().map(|s| s.entries()).unwrap_or(&[]) {
diff --git a/src/interpreter/runner.rs b/src/interpreter/runner.rs
index 42a90b1..fe477ec 100644
--- a/src/interpreter/runner.rs
+++ b/src/interpreter/runner.rs
@@ -18,8 +18,9 @@ use common::{DEFAULT_MEMORY_INDEX, DEFAULT_TABLE_INDEX, BlockFrame, BlockFrameTy
 use common::stack::StackWithLimit;
 
 /// Function interpreter.
-pub struct Interpreter<'store> {
+pub struct Interpreter<'store, St: 'static> {
 	store: &'store mut Store,
+	state: &'store mut St,
 }
 
 /// Function execution context.
@@ -64,10 +65,11 @@ enum RunResult {
 	NestedCall(FunctionContext),
 }
 
-impl<'store> Interpreter<'store> {
-	pub fn new(store: &mut Store) -> Interpreter {
+impl<'store, St: 'static> Interpreter<'store, St> {
+	pub fn new(store: &'store mut Store, state: &'store mut St) -> Interpreter<'store, St> {
 		Interpreter {
-			store
+			store,
+			state
 		}
 	}
 
@@ -95,7 +97,7 @@ impl<'store> Interpreter<'store> {
 					},
 					FuncInstance::Host { host_func, .. } => {
 						let args: Vec<_> = function_context.locals.drain(..).collect();
-						let result = self.store.invoke_host(host_func, args)?;
+						let result = self.store.invoke_host(self.state, host_func, args)?;
 						RunResult::Return(result)
 					},
 				}
diff --git a/src/interpreter/store.rs b/src/interpreter/store.rs
index b3cc024..f06a54f 100644
--- a/src/interpreter/store.rs
+++ b/src/interpreter/store.rs
@@ -2,6 +2,7 @@
 #![allow(unused)]
 
 use std::sync::Arc;
+use std::any::Any;
 use std::collections::HashMap;
 use elements::{FunctionType, GlobalEntry, GlobalType, InitExpr, MemoryType, Module,
                Opcode, Opcodes, Local, TableType, Type, Internal};
@@ -371,11 +372,11 @@ impl Store {
 		Ok(())
 	}
 
-	pub fn instantiate_module(
+	pub fn instantiate_module<St: 'static>(
 		&mut self,
 		module: &Module,
 		extern_vals: &[ExternVal],
-		start_exec_params: ExecutionParams,
+		start_exec_params: ExecutionParams<St>,
 	) -> Result<ModuleId, Error> {
 		let mut instance = ModuleInstance::new();
 		// Reserve the index of the module, but not yet push the module.
@@ -447,8 +448,8 @@ impl Store {
 		Ok(module_id)
 	}
 
-	fn invoke(&mut self, func: FuncId, params: ExecutionParams) -> Result<Option<RuntimeValue>, Error> {
-		let ExecutionParams { args } = params;
+	fn invoke<St>(&mut self, func: FuncId, params: ExecutionParams<St>) -> Result<Option<RuntimeValue>, Error> {
+		let ExecutionParams { args, mut state } = params;
 		let mut args = StackWithLimit::with_data(args, DEFAULT_VALUE_STACK_LIMIT);
 		let outer = CallerContext::topmost(&mut args);
 		let inner = {
@@ -457,11 +458,13 @@ impl Store {
 			let args = prepare_function_args(&func_signature, outer.value_stack)?;
 			FunctionContext::new(self, func, outer.value_stack_limit, outer.frame_stack_limit, &func_signature, args)
 		};
-		let mut interpreter = Interpreter::new(self);
+		let mut interpreter = Interpreter::new(self, &mut state);
 		interpreter.run_function(inner)
 	}
 
-	pub fn invoke_host(&mut self, host_func: HostFuncId, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error> {
+	pub fn invoke_host<St: 'static>(&mut self, state: &mut St, host_func: HostFuncId, args: Vec<RuntimeValue>) -> Result<Option<RuntimeValue>, Error> {
+		let host_func_instance = self.host_funcs.get(host_func.0 as usize).expect("ID should be always valid");
+		host_func_instance.call_as_any(state as &mut Any, &args);
 		panic!()
 	}