diff --git a/rpc/args.go b/rpc/args.go
index f560512422e091185c39dc640f2b7937b65855a8..ba2ef731aa17939871a938d9d0e2a03418912d41 100644
--- a/rpc/args.go
+++ b/rpc/args.go
@@ -47,7 +47,7 @@ func (args *GetBlockByNumberArgs) UnmarshalJSON(b []byte) (err error) {
 	if len(obj) < 1 {
 		return errArguments
 	}
-	args.BlockNumber = ethutil.BytesToNumber(fromHex(obj[0].(string)))
+	args.BlockNumber = uint64(ethutil.Big(obj[0].(string)).Int64())
 
 	if len(obj) > 1 {
 		args.Transactions = obj[1].(bool)
@@ -110,7 +110,7 @@ func (args *GetStorageArgs) UnmarshalJSON(b []byte) (err error) {
 	args.Address = obj[0].(string)
 
 	if len(obj) > 1 {
-		args.BlockNumber = ethutil.BytesToNumber(fromHex(obj[1].(string)))
+		args.BlockNumber = uint64(ethutil.Big(obj[1].(string)).Int64())
 	}
 
 	return nil
@@ -179,7 +179,7 @@ func (args *GetTxCountArgs) UnmarshalJSON(b []byte) (err error) {
 	args.Address = obj[0].(string)
 
 	if len(obj) > 1 {
-		args.BlockNumber = ethutil.BytesToNumber(fromHex(obj[1].(string)))
+		args.BlockNumber = uint64(ethutil.Big(obj[1].(string)).Int64())
 	}
 
 	return nil
@@ -210,7 +210,7 @@ func (args *GetBalanceArgs) UnmarshalJSON(b []byte) (err error) {
 	args.Address = obj[0].(string)
 
 	if len(obj) > 1 {
-		args.BlockNumber = ethutil.BytesToNumber(fromHex(obj[1].(string)))
+		args.BlockNumber = uint64(ethutil.Big(obj[1].(string)).Int64())
 	}
 
 	return nil
@@ -241,7 +241,7 @@ func (args *GetDataArgs) UnmarshalJSON(b []byte) (err error) {
 	args.Address = obj[0].(string)
 
 	if len(obj) > 1 {
-		args.BlockNumber = ethutil.BytesToNumber(fromHex(obj[1].(string)))
+		args.BlockNumber = uint64(ethutil.Big(obj[1].(string)).Int64())
 	}
 
 	return nil
@@ -299,10 +299,10 @@ func (args *FilterArgs) UnmarshalJSON(b []byte) (err error) {
 	if len(obj) < 1 {
 		return errArguments
 	}
-	args.FromBlock = ethutil.BytesToNumber(fromHex(obj[0].FromBlock))
-	args.ToBlock = ethutil.BytesToNumber(fromHex(obj[0].ToBlock))
-	args.Limit = ethutil.BytesToNumber(fromHex(obj[0].Limit))
-	args.Offset = ethutil.BytesToNumber(fromHex(obj[0].Offset))
+	args.FromBlock = uint64(ethutil.Big(obj[0].FromBlock).Int64())
+	args.ToBlock = uint64(ethutil.Big(obj[0].ToBlock).Int64())
+	args.Limit = uint64(ethutil.Big(obj[0].Limit).Int64())
+	args.Offset = uint64(ethutil.Big(obj[0].Offset).Int64())
 	args.Address = obj[0].Address
 	args.Topics = obj[0].Topics
 
@@ -335,10 +335,10 @@ func (args *FilterOptions) UnmarshalJSON(b []byte) (err error) {
 	if len(obj) < 1 {
 		return errArguments
 	}
-	args.Earliest = int64(ethutil.BytesToNumber(fromHex(obj[0].FromBlock)))
-	args.Latest = int64(ethutil.BytesToNumber(fromHex(obj[0].ToBlock)))
-	args.Max = int(ethutil.BytesToNumber(fromHex(obj[0].Limit)))
-	args.Skip = int(ethutil.BytesToNumber(fromHex(obj[0].Offset)))
+	args.Earliest = int64(ethutil.Big(obj[0].FromBlock).Int64())
+	args.Latest = int64(ethutil.Big(obj[0].ToBlock).Int64())
+	args.Max = int(ethutil.Big(obj[0].Limit).Int64())
+	args.Skip = int(ethutil.Big(obj[0].Offset).Int64())
 	args.Address = obj[0].Address
 	args.Topic = obj[0].Topics
 
diff --git a/rpc/args_test.go b/rpc/args_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..380ed176b32e3e1b313110e846259a0a7521ecc2
--- /dev/null
+++ b/rpc/args_test.go
@@ -0,0 +1,125 @@
+package rpc
+
+import (
+	"bytes"
+	"encoding/json"
+	"math/big"
+	"testing"
+)
+
+func TestSha3(t *testing.T) {
+	input := `["0x68656c6c6f20776f726c64"]`
+	expected := "0x68656c6c6f20776f726c64"
+
+	args := new(Sha3Args)
+	json.Unmarshal([]byte(input), &args)
+
+	if args.Data != expected {
+		t.Error("got %s expected %s", input, expected)
+	}
+}
+
+func TestGetBalanceArgs(t *testing.T) {
+	input := `["0x407d73d8a49eeb85d32cf465507dd71d507100c1", "0x1f"]`
+	expected := new(GetBalanceArgs)
+	expected.Address = "0x407d73d8a49eeb85d32cf465507dd71d507100c1"
+	expected.BlockNumber = 31
+
+	args := new(GetBalanceArgs)
+	if err := json.Unmarshal([]byte(input), &args); err != nil {
+		t.Error(err)
+	}
+
+	if args.Address != expected.Address {
+		t.Errorf("Address should be %v but is %v", expected.Address, args.Address)
+	}
+
+	if args.BlockNumber != expected.BlockNumber {
+		t.Errorf("BlockNumber should be %v but is %v", expected.BlockNumber, args.BlockNumber)
+	}
+}
+
+func TestGetBlockByHashArgs(t *testing.T) {
+	input := `["0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331", true]`
+	expected := new(GetBlockByHashArgs)
+	expected.BlockHash = "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331"
+	expected.Transactions = true
+
+	args := new(GetBlockByHashArgs)
+	if err := json.Unmarshal([]byte(input), &args); err != nil {
+		t.Error(err)
+	}
+
+	if args.BlockHash != expected.BlockHash {
+		t.Errorf("BlockHash should be %v but is %v", expected.BlockHash, args.BlockHash)
+	}
+
+	if args.Transactions != expected.Transactions {
+		t.Errorf("Transactions should be %v but is %v", expected.Transactions, args.Transactions)
+	}
+}
+
+func TestGetBlockByNumberArgs(t *testing.T) {
+	input := `["0x1b4", false]`
+	expected := new(GetBlockByNumberArgs)
+	expected.BlockNumber = 436
+	expected.Transactions = false
+
+	args := new(GetBlockByNumberArgs)
+	if err := json.Unmarshal([]byte(input), &args); err != nil {
+		t.Error(err)
+	}
+
+	if args.BlockNumber != expected.BlockNumber {
+		t.Errorf("BlockHash should be %v but is %v", expected.BlockNumber, args.BlockNumber)
+	}
+
+	if args.Transactions != expected.Transactions {
+		t.Errorf("Transactions should be %v but is %v", expected.Transactions, args.Transactions)
+	}
+}
+
+func TestNewTxArgs(t *testing.T) {
+	input := `[{"from": "0xb60e8dd61c5d32be8058bb8eb970870f07233155",
+  "to": "0xd46e8dd67c5d32be8058bb8eb970870f072445675",
+  "gas": "0x76c0",
+  "gasPrice": "0x9184e72a000",
+  "value": "0x9184e72a000",
+  "data": "0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675"}]`
+	expected := new(NewTxArgs)
+	expected.From = "0xb60e8dd61c5d32be8058bb8eb970870f07233155"
+	expected.To = "0xd46e8dd67c5d32be8058bb8eb970870f072445675"
+	expected.Gas = big.NewInt(30400)
+	expected.GasPrice = big.NewInt(10000000000000)
+	expected.Value = big.NewInt(10000000000000)
+	expected.Data = "0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675"
+
+	args := new(NewTxArgs)
+	if err := json.Unmarshal([]byte(input), &args); err != nil {
+		t.Error(err)
+	}
+
+	if expected.From != args.From {
+		t.Errorf("From shoud be %#v but is %#v", expected.From, args.From)
+	}
+
+	if expected.To != args.To {
+		t.Errorf("To shoud be %#v but is %#v", expected.To, args.To)
+	}
+
+	if bytes.Compare(expected.Gas.Bytes(), args.Gas.Bytes()) != 0 {
+		t.Errorf("Gas shoud be %#v but is %#v", expected.Gas.Bytes(), args.Gas.Bytes())
+	}
+
+	if bytes.Compare(expected.GasPrice.Bytes(), args.GasPrice.Bytes()) != 0 {
+		t.Errorf("GasPrice shoud be %#v but is %#v", expected.GasPrice, args.GasPrice)
+	}
+
+	if bytes.Compare(expected.Value.Bytes(), args.Value.Bytes()) != 0 {
+		t.Errorf("Value shoud be %#v but is %#v", expected.Value, args.Value)
+	}
+
+	if expected.Data != args.Data {
+		t.Errorf("Data shoud be %#v but is %#v", expected.Data, args.Data)
+	}
+}