diff --git a/src/int.rs b/src/int.rs
index aad0091..45e4f5c 100644
--- a/src/int.rs
+++ b/src/int.rs
@@ -1,4 +1,5 @@
 use core::ops::{Not, BitAnd, BitOr, BitXor, Shl, Shr};
+#[cfg(feature = "std")]
 use std::fmt::{Debug, Display};
 
 use {Num, NumCast};
@@ -6,6 +7,7 @@ use bounds::Bounded;
 use ops::checked::*;
 use ops::saturating::Saturating;
 
+#[cfg(feature = "std")]
 pub trait PrimInt
     : Sized
     + Copy
@@ -280,6 +282,280 @@ pub trait PrimInt
     fn pow(self, exp: u32) -> Self;
 }
 
+
+#[cfg(not(feature = "std"))]
+pub trait PrimInt
+    : Sized
+    + Copy
+    + Num + NumCast
+    + Bounded
+    + PartialOrd + Ord + Eq
+    + Not<Output=Self>
+    + BitAnd<Output=Self>
+    + BitOr<Output=Self>
+    + BitXor<Output=Self>
+    + Shl<usize, Output=Self>
+    + Shr<usize, Output=Self>
+    + CheckedAdd<Output=Self>
+    + CheckedSub<Output=Self>
+    + CheckedMul<Output=Self>
+    + CheckedDiv<Output=Self>
+    + Saturating
+{
+    /// Returns the number of ones in the binary representation of `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0b01001100u8;
+    ///
+    /// assert_eq!(n.count_ones(), 3);
+    /// ```
+    fn count_ones(self) -> u32;
+
+    /// Returns the number of zeros in the binary representation of `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0b01001100u8;
+    ///
+    /// assert_eq!(n.count_zeros(), 5);
+    /// ```
+    fn count_zeros(self) -> u32;
+
+    /// Returns the number of leading zeros in the binary representation
+    /// of `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0b0101000u16;
+    ///
+    /// assert_eq!(n.leading_zeros(), 10);
+    /// ```
+    fn leading_zeros(self) -> u32;
+
+    /// Returns the number of trailing zeros in the binary representation
+    /// of `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0b0101000u16;
+    ///
+    /// assert_eq!(n.trailing_zeros(), 3);
+    /// ```
+    fn trailing_zeros(self) -> u32;
+
+    /// Shifts the bits to the left by a specified amount amount, `n`, wrapping
+    /// the truncated bits to the end of the resulting integer.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFu64;
+    /// let m = 0x3456789ABCDEF012u64;
+    ///
+    /// assert_eq!(n.rotate_left(12), m);
+    /// ```
+    fn rotate_left(self, n: u32) -> Self;
+
+    /// Shifts the bits to the right by a specified amount amount, `n`, wrapping
+    /// the truncated bits to the beginning of the resulting integer.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFu64;
+    /// let m = 0xDEF0123456789ABCu64;
+    ///
+    /// assert_eq!(n.rotate_right(12), m);
+    /// ```
+    fn rotate_right(self, n: u32) -> Self;
+
+    /// Shifts the bits to the left by a specified amount amount, `n`, filling
+    /// zeros in the least significant bits.
+    ///
+    /// This is bitwise equivalent to signed `Shl`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFu64;
+    /// let m = 0x3456789ABCDEF000u64;
+    ///
+    /// assert_eq!(n.signed_shl(12), m);
+    /// ```
+    fn signed_shl(self, n: u32) -> Self;
+
+    /// Shifts the bits to the right by a specified amount amount, `n`, copying
+    /// the "sign bit" in the most significant bits even for unsigned types.
+    ///
+    /// This is bitwise equivalent to signed `Shr`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0xFEDCBA9876543210u64;
+    /// let m = 0xFFFFEDCBA9876543u64;
+    ///
+    /// assert_eq!(n.signed_shr(12), m);
+    /// ```
+    fn signed_shr(self, n: u32) -> Self;
+
+    /// Shifts the bits to the left by a specified amount amount, `n`, filling
+    /// zeros in the least significant bits.
+    ///
+    /// This is bitwise equivalent to unsigned `Shl`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFi64;
+    /// let m = 0x3456789ABCDEF000i64;
+    ///
+    /// assert_eq!(n.unsigned_shl(12), m);
+    /// ```
+    fn unsigned_shl(self, n: u32) -> Self;
+
+    /// Shifts the bits to the right by a specified amount amount, `n`, filling
+    /// zeros in the most significant bits.
+    ///
+    /// This is bitwise equivalent to unsigned `Shr`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0xFEDCBA9876543210i64;
+    /// let m = 0x000FEDCBA9876543i64;
+    ///
+    /// assert_eq!(n.unsigned_shr(12), m);
+    /// ```
+    fn unsigned_shr(self, n: u32) -> Self;
+
+    /// Reverses the byte order of the integer.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFu64;
+    /// let m = 0xEFCDAB8967452301u64;
+    ///
+    /// assert_eq!(n.swap_bytes(), m);
+    /// ```
+    fn swap_bytes(self) -> Self;
+
+    /// Convert an integer from big endian to the target's endianness.
+    ///
+    /// On big endian this is a no-op. On little endian the bytes are swapped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFu64;
+    ///
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(u64::from_be(n), n)
+    /// } else {
+    ///     assert_eq!(u64::from_be(n), n.swap_bytes())
+    /// }
+    /// ```
+    fn from_be(x: Self) -> Self;
+
+    /// Convert an integer from little endian to the target's endianness.
+    ///
+    /// On little endian this is a no-op. On big endian the bytes are swapped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFu64;
+    ///
+    /// if cfg!(target_endian = "little") {
+    ///     assert_eq!(u64::from_le(n), n)
+    /// } else {
+    ///     assert_eq!(u64::from_le(n), n.swap_bytes())
+    /// }
+    /// ```
+    fn from_le(x: Self) -> Self;
+
+    /// Convert `self` to big endian from the target's endianness.
+    ///
+    /// On big endian this is a no-op. On little endian the bytes are swapped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFu64;
+    ///
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(n.to_be(), n)
+    /// } else {
+    ///     assert_eq!(n.to_be(), n.swap_bytes())
+    /// }
+    /// ```
+    fn to_be(self) -> Self;
+
+    /// Convert `self` to little endian from the target's endianness.
+    ///
+    /// On little endian this is a no-op. On big endian the bytes are swapped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// let n = 0x0123456789ABCDEFu64;
+    ///
+    /// if cfg!(target_endian = "little") {
+    ///     assert_eq!(n.to_le(), n)
+    /// } else {
+    ///     assert_eq!(n.to_le(), n.swap_bytes())
+    /// }
+    /// ```
+    fn to_le(self) -> Self;
+
+    /// Raises self to the power of `exp`, using exponentiation by squaring.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::PrimInt;
+    ///
+    /// assert_eq!(2i32.pow(4), 16);
+    /// ```
+    fn pow(self, exp: u32) -> Self;
+}
+
 macro_rules! prim_int_impl {
     ($T:ty, $S:ty, $U:ty) => (
         impl PrimInt for $T {