diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index befe8ebb5..7a9888b5d 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -37,15 +37,21 @@ use extras::TransactionAddress;
 pub use blockchain::TreeRoute;
 
 /// Uniquely identifies block.
+#[derive(Debug, PartialEq)]
 pub enum BlockId {
 	/// Block's sha3.
 	/// Querying by hash is always faster.
 	Hash(H256),
 	/// Block number within canon blockchain.
-	Number(BlockNumber)
+	Number(BlockNumber),
+	/// Earliest block (genesis).
+	Earliest,
+	/// Latest mined block.
+	Latest
 }
 
 /// Uniquely identifies transaction.
+#[derive(Debug, PartialEq)]
 pub enum TransactionId {
 	/// Transaction's sha3.
 	Hash(H256),
@@ -347,7 +353,9 @@ impl Client {
 	fn block_hash(&self, id: BlockId) -> Option<H256> {
 		match id {
 			BlockId::Hash(hash) => Some(hash),
-			BlockId::Number(number) => self.chain.read().unwrap().block_hash(number)
+			BlockId::Number(number) => self.chain.read().unwrap().block_hash(number),
+			BlockId::Earliest => self.chain.read().unwrap().block_hash(0),
+			BlockId::Latest => Some(self.chain.read().unwrap().best_block_hash())
 		}
 	}
 }
diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index d9f65adc0..204a4a257 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -183,8 +183,12 @@ impl Eth for EthClient {
 			})
 	}
 
-	fn transaction_by_block_number_and_index(&self, _params: Params) -> Result<Value, Error> {
-		unimplemented!()
+	fn transaction_by_block_number_and_index(&self, params: Params) -> Result<Value, Error> {
+		from_params::<(BlockNumber, Index)>(params)
+			.and_then(|(number, index)| match self.client.transaction(TransactionId::Location(number.into(), index.value())) {
+				Some(t) => to_value(&Transaction::from(t)),
+				None => Ok(Value::Null)
+			})
 	}
 }
 
diff --git a/rpc/src/v1/types/block_number.rs b/rpc/src/v1/types/block_number.rs
index bfe20f177..b524d8450 100644
--- a/rpc/src/v1/types/block_number.rs
+++ b/rpc/src/v1/types/block_number.rs
@@ -16,6 +16,7 @@
 
 use serde::{Deserialize, Deserializer, Error};
 use serde::de::Visitor;
+use ethcore::client::BlockId;
 
 /// Represents rpc api block number param.
 #[derive(Debug, PartialEq)]
@@ -53,8 +54,20 @@ impl Visitor for BlockNumberVisitor {
 	}
 }
 
+impl Into<BlockId> for BlockNumber {
+	fn into(self) -> BlockId {
+		match self {
+			BlockNumber::Num(n) => BlockId::Number(n),
+			BlockNumber::Earliest => BlockId::Earliest,
+			BlockNumber::Latest => BlockId::Latest,
+			BlockNumber::Pending => BlockId::Latest // TODO: change this once blockid support pending
+		}
+	}
+}
+
 #[cfg(test)]
 mod tests {
+	use ethcore::client::BlockId;
 	use super::*;
 	use serde_json;
 
@@ -64,5 +77,13 @@ mod tests {
 		let deserialized: Vec<BlockNumber> = serde_json::from_str(s).unwrap();
 		assert_eq!(deserialized, vec![BlockNumber::Num(10), BlockNumber::Num(10), BlockNumber::Latest, BlockNumber::Earliest, BlockNumber::Pending])
 	}
+
+	#[test]
+	fn block_number_into() {
+		assert_eq!(BlockId::Number(100), BlockNumber::Num(100).into());
+		assert_eq!(BlockId::Earliest, BlockNumber::Earliest.into());
+		assert_eq!(BlockId::Latest, BlockNumber::Latest.into());
+		assert_eq!(BlockId::Latest, BlockNumber::Pending.into());
+	}
 }
 
diff --git a/sync/src/tests/helpers.rs b/sync/src/tests/helpers.rs
index 384b5bd65..d8cd5e54a 100644
--- a/sync/src/tests/helpers.rs
+++ b/sync/src/tests/helpers.rs
@@ -80,7 +80,9 @@ impl TestBlockChainClient {
 	fn block_hash(&self, id: BlockId) -> Option<H256> {
 		match id {
 			BlockId::Hash(hash) => Some(hash),
-			BlockId::Number(n) => self.numbers.read().unwrap().get(&(n as usize)).cloned()
+			BlockId::Number(n) => self.numbers.read().unwrap().get(&(n as usize)).cloned(),
+			BlockId::Earliest => self.numbers.read().unwrap().get(&0).cloned(),
+			BlockId::Latest => self.numbers.read().unwrap().get(&(self.numbers.read().unwrap().len() - 1)).cloned()
 		}
 	}
 }