diff --git a/src/mat.rs b/src/mat.rs
index 0d4112f..6fcd9ac 100644
--- a/src/mat.rs
+++ b/src/mat.rs
@@ -100,6 +100,7 @@ pub trait NumericMatrixNxN<T, ColRow>: MatrixNxN<T, ColRow>,
     pure fn mul_m(other: &self) -> self;
     
     pure fn det() -> T;
+    pure fn trace() -> T;
     
     pure fn invert() -> Option<self>;
     pure fn transpose() -> self;
@@ -266,6 +267,10 @@ pub impl<T:Copy Num NumCast DefaultEq> Mat2<T>: NumericMatrixNxN<T, Vec2<T>> {
        self[0][0] * self[1][1] - self[1][0] * self[0][1]
     }
 
+    pure fn trace() -> T {
+        self[0][0] + self[1][1]
+    }
+
     #[inline(always)]
     pure fn invert() -> Option<Mat2<T>> {
         let _0 = cast(0);
@@ -508,6 +513,10 @@ pub impl<T:Copy Num NumCast DefaultEq> Mat3<T>: NumericMatrixNxN<T, Vec3<T>> {
         self.col(0).dot(&self.col(1).cross(&self.col(2)))
     }
 
+    pure fn trace() -> T {
+        self[0][0] + self[1][1] + self[2][2]
+    }
+
     // #[inline(always)]
     pure fn invert() -> Option<Mat3<T>> {
         let d = self.det();
@@ -566,14 +575,14 @@ pub impl<T:Copy NumCast> Mat3<T>: NumericMatrix3x3<T, Vec3<T>> {
     }
 }
 
-pub impl<T:Copy Num NumCast Ord> Mat3<T>: ToQuat<T> {
+pub impl<T:Copy Num NumCast Ord DefaultEq> Mat3<T>: ToQuat<T> {
     pure fn to_Quat() -> Quat<T> {
         // Implemented using a mix of ideas from jMonkeyEngine and Ken Shoemake's
         // paper on Quaternions: http://www.cs.ucr.edu/~vbz/resources/Quatut.pdf
         
         let mut s: float;
         let w: float, x: float, y: float, z: float;
-        let trace: float = cast(self[0][0] + self[1][1] + self[2][2]);
+        let trace: float = cast(self.trace());
         
         if trace >= cast(0) {
             s = (trace + 1f).sqrt();
@@ -843,6 +852,10 @@ pub impl<T:Copy Num NumCast DefaultEq Signed Ord> Mat4<T>: NumericMatrixNxN<T, V
                              self[0][3], self[1][3], self[2][3]).det()
     }
 
+    pure fn trace() -> T {
+        self[0][0] + self[1][1] + self[2][2] + self[3][3]
+    }
+
     pure fn invert() -> Option<Mat4<T>> {
         let d = self.det();
         let _0 = cast(0);
diff --git a/src/test/test_mat.rs b/src/test/test_mat.rs
index 36b4d23..1892618 100644
--- a/src/test/test_mat.rs
+++ b/src/test/test_mat.rs
@@ -31,6 +31,7 @@ fn test_Mat2() {
     assert a.col(1) == Vec2::new(2f, 4f);
 
     assert a.det() == -2f;
+    assert a.trace() == 5f;
     
     assert a.neg() == Mat2::new(-1f, -3f,
                                 -2f, -4f);
@@ -135,6 +136,7 @@ fn test_Mat3() {
     assert a.col(2) == Vec3::new(3f, 6f, 9f);
 
     assert a.det() == 0f;
+    assert a.trace() == 15f;
     
     assert a.neg() == Mat3::new(-1f, -4f, -7f,
                                 -2f, -5f, -8f,
@@ -269,6 +271,7 @@ fn test_Mat4() {
     assert a.col(3) == Vec4::new(4f, 8f, 12f, 16f);
 
     assert a.det() == 0f;
+    assert a.trace() == 34f;
     
     assert a.neg() == Mat4::new(-1f, -5f,  -9f, -13f,
                                 -2f, -6f, -10f, -14f,