diff --git a/accounts/abi/abi.go b/accounts/abi/abi.go
index 3704e6262..673088f60 100644
--- a/accounts/abi/abi.go
+++ b/accounts/abi/abi.go
@@ -56,17 +56,36 @@ func JSON(reader io.Reader) (ABI, error) {
 func (abi ABI) pack(name string, args ...interface{}) ([]byte, error) {
 	method := abi.Methods[name]
 
+	// variable input is the output appended at the end of packed
+	// output. This is used for strings and bytes types input.
+	var variableInput []byte
+
 	var ret []byte
 	for i, a := range args {
 		input := method.Inputs[i]
-
+		// pack the input
 		packed, err := input.Type.pack(a)
 		if err != nil {
 			return nil, fmt.Errorf("`%s` %v", name, err)
 		}
-		ret = append(ret, packed...)
 
+		// check for a string or bytes input type
+		switch input.Type.T {
+		case StringTy, BytesTy:
+			// calculate the offset
+			offset := len(method.Inputs)*32 + len(variableInput)
+			// set the offset
+			ret = append(ret, packNum(reflect.ValueOf(offset), UintTy)...)
+			// Append the packed output to the variable input. The variable input
+			// will be appended at the end of the input.
+			variableInput = append(variableInput, packed...)
+		default:
+			// append the packed value to the input
+			ret = append(ret, packed...)
+		}
 	}
+	// append the variable input at the end of the packed input
+	ret = append(ret, variableInput...)
 
 	return ret, nil
 }
diff --git a/accounts/abi/abi_test.go b/accounts/abi/abi_test.go
index d1b8330e3..170f3f74b 100644
--- a/accounts/abi/abi_test.go
+++ b/accounts/abi/abi_test.go
@@ -365,6 +365,134 @@ func ExampleJSON() {
 	// 1f2c40920000000000000000000000000000000000000000000000000000000000000001
 }
 
+func TestInputVariableInputLength(t *testing.T) {
+	const definition = `[
+	{ "type" : "function", "name" : "strOne", "const" : true, "inputs" : [ { "name" : "str", "type" : "string" } ] },
+	{ "type" : "function", "name" : "bytesOne", "const" : true, "inputs" : [ { "name" : "str", "type" : "bytes" } ] },
+	{ "type" : "function", "name" : "strTwo", "const" : true, "inputs" : [ { "name" : "str", "type" : "string" }, { "name" : "str1", "type" : "string" } ] }
+]`
+
+	abi, err := JSON(strings.NewReader(definition))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// test one string
+	strin := "hello world"
+	strpack, err := abi.Pack("strOne", strin)
+	if err != nil {
+		t.Error(err)
+	}
+
+	offset := make([]byte, 32)
+	offset[31] = 32
+	length := make([]byte, 32)
+	length[31] = byte(len(strin))
+	value := common.RightPadBytes([]byte(strin), 32)
+	exp := append(offset, append(length, value...)...)
+
+	// ignore first 4 bytes of the output. This is the function identifier
+	strpack = strpack[4:]
+	if !bytes.Equal(strpack, exp) {
+		t.Errorf("expected %x, got %x\n", exp, strpack)
+	}
+
+	// test one bytes
+	btspack, err := abi.Pack("bytesOne", []byte(strin))
+	if err != nil {
+		t.Error(err)
+	}
+	// ignore first 4 bytes of the output. This is the function identifier
+	btspack = btspack[4:]
+	if !bytes.Equal(btspack, exp) {
+		t.Errorf("expected %x, got %x\n", exp, btspack)
+	}
+
+	//  test two strings
+	str1 := "hello"
+	str2 := "world"
+	str2pack, err := abi.Pack("strTwo", str1, str2)
+	if err != nil {
+		t.Error(err)
+	}
+
+	offset1 := make([]byte, 32)
+	offset1[31] = 64
+	length1 := make([]byte, 32)
+	length1[31] = byte(len(str1))
+	value1 := common.RightPadBytes([]byte(str1), 32)
+
+	offset2 := make([]byte, 32)
+	offset2[31] = 128
+	length2 := make([]byte, 32)
+	length2[31] = byte(len(str2))
+	value2 := common.RightPadBytes([]byte(str2), 32)
+
+	exp2 := append(offset1, offset2...)
+	exp2 = append(exp2, append(length1, value1...)...)
+	exp2 = append(exp2, append(length2, value2...)...)
+
+	// ignore first 4 bytes of the output. This is the function identifier
+	str2pack = str2pack[4:]
+	if !bytes.Equal(str2pack, exp2) {
+		t.Errorf("expected %x, got %x\n", exp, str2pack)
+	}
+
+	// test two strings, first > 32, second < 32
+	str1 = strings.Repeat("a", 33)
+	str2pack, err = abi.Pack("strTwo", str1, str2)
+	if err != nil {
+		t.Error(err)
+	}
+
+	offset1 = make([]byte, 32)
+	offset1[31] = 64
+	length1 = make([]byte, 32)
+	length1[31] = byte(len(str1))
+	value1 = common.RightPadBytes([]byte(str1), 64)
+	offset2[31] = 160
+
+	exp2 = append(offset1, offset2...)
+	exp2 = append(exp2, append(length1, value1...)...)
+	exp2 = append(exp2, append(length2, value2...)...)
+
+	// ignore first 4 bytes of the output. This is the function identifier
+	str2pack = str2pack[4:]
+	if !bytes.Equal(str2pack, exp2) {
+		t.Errorf("expected %x, got %x\n", exp, str2pack)
+	}
+
+	// test two strings, first > 32, second >32
+	str1 = strings.Repeat("a", 33)
+	str2 = strings.Repeat("a", 33)
+	str2pack, err = abi.Pack("strTwo", str1, str2)
+	if err != nil {
+		t.Error(err)
+	}
+
+	offset1 = make([]byte, 32)
+	offset1[31] = 64
+	length1 = make([]byte, 32)
+	length1[31] = byte(len(str1))
+	value1 = common.RightPadBytes([]byte(str1), 64)
+
+	offset2 = make([]byte, 32)
+	offset2[31] = 160
+	length2 = make([]byte, 32)
+	length2[31] = byte(len(str2))
+	value2 = common.RightPadBytes([]byte(str2), 64)
+
+	exp2 = append(offset1, offset2...)
+	exp2 = append(exp2, append(length1, value1...)...)
+	exp2 = append(exp2, append(length2, value2...)...)
+
+	// ignore first 4 bytes of the output. This is the function identifier
+	str2pack = str2pack[4:]
+	if !bytes.Equal(str2pack, exp2) {
+		t.Errorf("expected %x, got %x\n", exp, str2pack)
+	}
+}
+
 func TestBytes(t *testing.T) {
 	const definition = `[
 	{ "type" : "function", "name" : "balance", "const" : true, "inputs" : [ { "name" : "address", "type" : "bytes20" } ] },
diff --git a/accounts/abi/numbers.go b/accounts/abi/numbers.go
index c37cd5f68..02609d567 100644
--- a/accounts/abi/numbers.go
+++ b/accounts/abi/numbers.go
@@ -23,36 +23,38 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 )
 
-var big_t = reflect.TypeOf(&big.Int{})
-var ubig_t = reflect.TypeOf(&big.Int{})
-var byte_t = reflect.TypeOf(byte(0))
-var byte_ts = reflect.TypeOf([]byte(nil))
-var uint_t = reflect.TypeOf(uint(0))
-var uint8_t = reflect.TypeOf(uint8(0))
-var uint16_t = reflect.TypeOf(uint16(0))
-var uint32_t = reflect.TypeOf(uint32(0))
-var uint64_t = reflect.TypeOf(uint64(0))
-var int_t = reflect.TypeOf(int(0))
-var int8_t = reflect.TypeOf(int8(0))
-var int16_t = reflect.TypeOf(int16(0))
-var int32_t = reflect.TypeOf(int32(0))
-var int64_t = reflect.TypeOf(int64(0))
-var hash_t = reflect.TypeOf(common.Hash{})
-var address_t = reflect.TypeOf(common.Address{})
+var (
+	big_t     = reflect.TypeOf(&big.Int{})
+	ubig_t    = reflect.TypeOf(&big.Int{})
+	byte_t    = reflect.TypeOf(byte(0))
+	byte_ts   = reflect.TypeOf([]byte(nil))
+	uint_t    = reflect.TypeOf(uint(0))
+	uint8_t   = reflect.TypeOf(uint8(0))
+	uint16_t  = reflect.TypeOf(uint16(0))
+	uint32_t  = reflect.TypeOf(uint32(0))
+	uint64_t  = reflect.TypeOf(uint64(0))
+	int_t     = reflect.TypeOf(int(0))
+	int8_t    = reflect.TypeOf(int8(0))
+	int16_t   = reflect.TypeOf(int16(0))
+	int32_t   = reflect.TypeOf(int32(0))
+	int64_t   = reflect.TypeOf(int64(0))
+	hash_t    = reflect.TypeOf(common.Hash{})
+	address_t = reflect.TypeOf(common.Address{})
 
-var uint_ts = reflect.TypeOf([]uint(nil))
-var uint8_ts = reflect.TypeOf([]uint8(nil))
-var uint16_ts = reflect.TypeOf([]uint16(nil))
-var uint32_ts = reflect.TypeOf([]uint32(nil))
-var uint64_ts = reflect.TypeOf([]uint64(nil))
-var ubig_ts = reflect.TypeOf([]*big.Int(nil))
+	uint_ts   = reflect.TypeOf([]uint(nil))
+	uint8_ts  = reflect.TypeOf([]uint8(nil))
+	uint16_ts = reflect.TypeOf([]uint16(nil))
+	uint32_ts = reflect.TypeOf([]uint32(nil))
+	uint64_ts = reflect.TypeOf([]uint64(nil))
+	ubig_ts   = reflect.TypeOf([]*big.Int(nil))
 
-var int_ts = reflect.TypeOf([]int(nil))
-var int8_ts = reflect.TypeOf([]int8(nil))
-var int16_ts = reflect.TypeOf([]int16(nil))
-var int32_ts = reflect.TypeOf([]int32(nil))
-var int64_ts = reflect.TypeOf([]int64(nil))
-var big_ts = reflect.TypeOf([]*big.Int(nil))
+	int_ts   = reflect.TypeOf([]int(nil))
+	int8_ts  = reflect.TypeOf([]int8(nil))
+	int16_ts = reflect.TypeOf([]int16(nil))
+	int32_ts = reflect.TypeOf([]int32(nil))
+	int64_ts = reflect.TypeOf([]int64(nil))
+	big_ts   = reflect.TypeOf([]*big.Int(nil))
+)
 
 // U256 will ensure unsigned 256bit on big nums
 func U256(n *big.Int) []byte {
diff --git a/accounts/abi/type.go b/accounts/abi/type.go
index 6fb2950ba..c08b744f7 100644
--- a/accounts/abi/type.go
+++ b/accounts/abi/type.go
@@ -163,6 +163,13 @@ func (t Type) String() (out string) {
 	return t.stringKind
 }
 
+// packBytesSlice packs the given bytes as [L, V] as the canonical representation
+// bytes slice
+func packBytesSlice(bytes []byte, l int) []byte {
+	len := packNum(reflect.ValueOf(l), UintTy)
+	return append(len, common.RightPadBytes(bytes, (l+31)/32*32)...)
+}
+
 // Test the given input parameter `v` and checks if it matches certain
 // criteria
 // * Big integers are checks for ptr types and if the given value is
@@ -193,8 +200,14 @@ func (t Type) pack(v interface{}) ([]byte, error) {
 		if t.Size > -1 && value.Len() > t.Size {
 			return nil, fmt.Errorf("%v out of bound. %d for %d", value.Kind(), value.Len(), t.Size)
 		}
-		return []byte(common.LeftPadString(t.String(), 32)), nil
+
+		return packBytesSlice([]byte(value.String()), value.Len()), nil
 	case reflect.Slice:
+		// if the param is a bytes type, pack the slice up as a string
+		if t.T == BytesTy {
+			return packBytesSlice(value.Bytes(), value.Len()), nil
+		}
+
 		if t.Size > -1 && value.Len() > t.Size {
 			return nil, fmt.Errorf("%v out of bound. %d for %d", value.Kind(), value.Len(), t.Size)
 		}