diff --git a/src/bytes.rs b/src/bytes.rs
index 06735995f..52dad3cb9 100644
--- a/src/bytes.rs
+++ b/src/bytes.rs
@@ -8,6 +8,7 @@
 
 use std::fmt;
 use std::error::Error as StdError;
+use uint::{U128, U256};
 
 /// TODO: optimise some conversations
 pub trait ToBytes {
@@ -82,6 +83,26 @@ impl_map_to_bytes!(usize, u64);
 impl_map_to_bytes!(u16, u64);
 impl_map_to_bytes!(u32, u64);
 
+macro_rules! impl_uint_to_bytes {
+    ($name: ident) => {
+        impl ToBytes for $name {
+            fn to_bytes(&self) -> Vec<u8> { 
+                let mut res= vec![];
+                let count = self.to_bytes_len();
+                for i in 0..count {
+                    let j = count - 1 - i;
+                    res.push(self.byte(j));
+                }
+                res
+            }
+            fn to_bytes_len(&self) -> usize { (self.bits() + 7) / 8 }
+        }
+    }
+}
+
+impl_uint_to_bytes!(U256);
+impl_uint_to_bytes!(U128);
+
 #[derive(Debug, PartialEq, Eq)]
 pub enum FromBytesError {
     UnexpectedEnd
@@ -101,6 +122,7 @@ pub type FromBytesResult<T> = Result<T, FromBytesError>;
 
 /// implements "Sized", so the compiler can deducate the size
 /// of the return type
+/// TODO: check size of bytes before conversation and return appropriate error
 pub trait FromBytes: Sized {
     fn from_bytes(bytes: &[u8]) -> FromBytesResult<Self>;
 }
@@ -149,3 +171,16 @@ macro_rules! impl_map_from_bytes {
 impl_map_from_bytes!(usize, u64);
 impl_map_from_bytes!(u16, u64);
 impl_map_from_bytes!(u32, u64);
+
+macro_rules! impl_uint_from_bytes {
+    ($name: ident) => {
+        impl FromBytes for $name {
+            fn from_bytes(bytes: &[u8]) -> FromBytesResult<$name> {
+                Ok($name::from(bytes))
+            }
+        }
+    }
+}
+
+impl_uint_from_bytes!(U256);
+impl_uint_from_bytes!(U128);
diff --git a/src/rlp.rs b/src/rlp.rs
index cd83a8c7e..03a10348c 100644
--- a/src/rlp.rs
+++ b/src/rlp.rs
@@ -522,8 +522,10 @@ impl Encoder for BasicEncoder {
 #[cfg(test)]
 mod tests {
     use std::{fmt, cmp};
+    use std::str::FromStr;
     use rlp;
     use rlp::{Rlp, RlpStream, Decodable};
+    use uint::U256;
 
     #[test]
     fn rlp_at() {
@@ -643,6 +645,21 @@ mod tests {
         run_encode_tests(tests);
     }
 
+    #[test]
+    fn encode_u256() {
+        let tests = vec![
+            ETestPair(U256::from(0u64), vec![0x80u8]),
+            ETestPair(U256::from(0x1000000u64), vec![0x84, 0x01, 0x00, 0x00, 0x00]),
+            ETestPair(U256::from(0xffffffffu64), vec![0x84, 0xff, 0xff, 0xff, 0xff]),
+            ETestPair(U256::from_str("8090a0b0c0d0e0f00910203040506077000000000000000100000000000012f0").unwrap(),
+            vec![0xa0, 0x80, 0x90, 0xa0, 0xb0, 0xc0, 0xd0, 0xe0, 0xf0,
+                       0x09, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x77,
+                       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
+                       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x12, 0xf0])
+        ];
+        run_encode_tests(tests);
+    }
+
     #[test]
     fn encode_str() {
         let tests = vec![
@@ -769,6 +786,21 @@ mod tests {
         run_decode_tests(tests);
     }
 
+    #[test]
+    fn decode_u256() {
+        let tests = vec![
+            DTestPair(U256::from(0u64), vec![0x80u8]),
+            DTestPair(U256::from(0x1000000u64), vec![0x84, 0x01, 0x00, 0x00, 0x00]),
+            DTestPair(U256::from(0xffffffffu64), vec![0x84, 0xff, 0xff, 0xff, 0xff]),
+            DTestPair(U256::from_str("8090a0b0c0d0e0f00910203040506077000000000000000100000000000012f0").unwrap(),
+            vec![0xa0, 0x80, 0x90, 0xa0, 0xb0, 0xc0, 0xd0, 0xe0, 0xf0,
+                       0x09, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x77,
+                       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
+                       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x12, 0xf0])
+        ];
+        run_decode_tests(tests);
+    }
+
     #[test]
     fn decode_str() {
         let tests = vec![
diff --git a/src/uint.rs b/src/uint.rs
index 149ff5efb..daba98b63 100644
--- a/src/uint.rs
+++ b/src/uint.rs
@@ -180,6 +180,12 @@ macro_rules! construct_uint {
                 arr[index / 64] & (1 << (index % 64)) != 0
             }
 
+            #[inline]
+            pub fn byte(&self, index: usize) -> u8 {
+                let &$name(ref arr) = self;
+                (arr[index / 8] >> ((index % 8)) * 8) as u8
+            }
+
             /// Multiplication by u32
             fn mul_u32(self, other: u32) -> $name {
                 let $name(ref arr) = self;
@@ -507,6 +513,7 @@ mod tests {
 
     #[test]
     pub fn uint256_bits_test() {
+        assert_eq!(U256::from(0u64).bits(), 0);
         assert_eq!(U256::from(255u64).bits(), 8);
         assert_eq!(U256::from(256u64).bits(), 9);
         assert_eq!(U256::from(300u64).bits(), 9);
@@ -523,11 +530,22 @@ mod tests {
         assert_eq!(shl.bits(), 0);
 
         //// Bit set check
+        //// 01010
         assert!(!U256::from(10u8).bit(0));
         assert!(U256::from(10u8).bit(1));
         assert!(!U256::from(10u8).bit(2));
         assert!(U256::from(10u8).bit(3));
         assert!(!U256::from(10u8).bit(4));
+
+        //// byte check
+        assert_eq!(U256::from(10u8).byte(0), 10);
+        assert_eq!(U256::from(0xffu64).byte(0), 0xff);
+        assert_eq!(U256::from(0xffu64).byte(1), 0);
+        assert_eq!(U256::from(0x01ffu64).byte(0), 0xff);
+        assert_eq!(U256::from(0x01ffu64).byte(1), 0x1);
+        assert_eq!(U256([0u64, 0xfc, 0, 0]).byte(8), 0xfc);
+        assert_eq!(U256([0u64, 0, 0, u64::max_value()]).byte(31), 0xff);
+        assert_eq!(U256([0u64, 0, 0, (u64::max_value() >> 8) + 1]).byte(31), 0x01);
     }
 
     #[test]