diff --git a/ethcore/src/trace/executive_tracer.rs b/ethcore/src/trace/executive_tracer.rs
index a0bff1c72..41d8c2389 100644
--- a/ethcore/src/trace/executive_tracer.rs
+++ b/ethcore/src/trace/executive_tracer.rs
@@ -40,8 +40,7 @@ impl Tracer for ExecutiveTracer {
 		Some(vec![])
 	}
 
-	fn trace_call(&mut self, call: Option<Call>, gas_used: U256, output: Option<Bytes>, depth: usize, subs:
-				  Vec<Trace>, delegate_call: bool) {
+	fn trace_call(&mut self, call: Option<Call>, gas_used: U256, output: Option<Bytes>, depth: usize, subs: Vec<Trace>, delegate_call: bool) {
 		// don't trace if it's DELEGATECALL or CALLCODE.
 		if delegate_call {
 			return;
diff --git a/ethcore/src/trace/mod.rs b/ethcore/src/trace/mod.rs
index dd8cd4d20..21827dd58 100644
--- a/ethcore/src/trace/mod.rs
+++ b/ethcore/src/trace/mod.rs
@@ -81,13 +81,25 @@ pub trait Tracer: Send {
 	/// Stores failed create trace.
 	fn trace_failed_create(&mut self, create: Option<Create>, depth: usize, subs: Vec<Trace>);
 
-	/// Spawn subracer which will be used to trace deeper levels of execution.
+	/// Spawn subtracer which will be used to trace deeper levels of execution.
 	fn subtracer(&self) -> Self where Self: Sized;
 
 	/// Consumes self and returns all traces.
 	fn traces(self) -> Vec<Trace>;
 }
 
+/// Used by executive to build VM traces.
+pub trait VMTracer: Send {
+	/// Trace the preparation to execute a single instruction.
+	fn trace_prepare_execute(pc: usize, instruction: u8, gas_cost: &U256, stack: &Vec<U256>);
+
+	/// Spawn subtracer which will be used to trace deeper levels of execution.
+	fn subtracer(&self) -> Self where Self: Sized;
+
+	/// Consumes self and returns all VM traces.
+	fn traces(self) -> Vec<VMTrace>;
+}
+
 /// `DbExtras` provides an interface to query extra data which is not stored in tracesdb,
 /// but necessary to work correctly.
 pub trait DatabaseExtras {
diff --git a/ethcore/src/types/trace_types/trace.rs b/ethcore/src/types/trace_types/trace.rs
index da58f3253..5b5132643 100644
--- a/ethcore/src/types/trace_types/trace.rs
+++ b/ethcore/src/types/trace_types/trace.rs
@@ -349,6 +349,17 @@ impl Trace {
 	}
 }
 
+/*pub struct VMExecutedOperation {
+	/// The total gas used.
+	pub gas_used: U256,
+	/// Altered storage value.
+	pub storage_diff: Option<(U256, U256)>,
+	/// If altered, the new memory image.
+	pub new_memory: Option<Bytes>,
+}*/
+	/// Information concerning the execution of the operation.
+//	pub executed: Option<VMExecutedOperation>,
+
 #[derive(Debug, Clone, PartialEq, Binary)]
 /// A record of the execution of a single VM operation.
 pub struct VMOperation {
@@ -358,26 +369,17 @@ pub struct VMOperation {
 	pub instruction: u8,
 	/// The gas cost for this instruction.
 	pub gas_cost: U256,
-	/// The total gas used.
-	pub gas_used: U256,
 	/// The stack.
 	pub stack: Vec<U256>,
-	/// Altered storage value. TODO: should be option.
-//	pub storage_diff: Option<(U256, U256)>,
-	/// If altered, the new memory image.
-	pub new_memory: Bytes,
 }
 
 impl Encodable for VMOperation {
 	fn rlp_append(&self, s: &mut RlpStream) {
-		s.begin_list(6);
+		s.begin_list(4);
 		s.append(&self.pc);
 		s.append(&self.instruction);
 		s.append(&self.gas_cost);
-		s.append(&self.gas_used);
 		s.append(&self.stack);
-//		s.append(&self.storage_diff);
-		s.append(&self.new_memory);
 	}
 }
 
@@ -388,10 +390,7 @@ impl Decodable for VMOperation {
 			pc: try!(d.val_at(0)),
 			instruction: try!(d.val_at(1)),
 			gas_cost: try!(d.val_at(2)),
-			gas_used: try!(d.val_at(3)),
-			stack: try!(d.val_at(4)),
-//			storage_diff: try!(d.val_at(5)),
-			new_memory: try!(d.val_at(6)),
+			stack: try!(d.val_at(3)),
 		};
 
 		Ok(res)
diff --git a/rpc/src/v1/impls/ethcore.rs b/rpc/src/v1/impls/ethcore.rs
index d34c6d62e..4412cdac6 100644
--- a/rpc/src/v1/impls/ethcore.rs
+++ b/rpc/src/v1/impls/ethcore.rs
@@ -157,8 +157,6 @@ impl<C, M> Ethcore for EthcoreClient<C, M> where C: BlockChainClient + 'static,
 		to_value(&Bytes::new(version))
 	}
 
-	//pub type VMTraceFunctionBox = Box<FnMut(usize, u8, U256, U256) + Send>;
-
 	fn vm_trace_call(&self, params: Params) -> Result<Value, Error> {
 		trace!(target: "jsonrpc", "vm_trace_call: {:?}", params);
 		from_params(params)