diff --git a/src/matrix.rs b/src/matrix.rs
index 8b98632..3f28998 100644
--- a/src/matrix.rs
+++ b/src/matrix.rs
@@ -161,6 +161,8 @@ impl<S: BaseFloat> Matrix3<S> {
     }
 
     /// Create a rotation matrix from an angle around an arbitrary axis.
+    ///
+    /// The specified axis **must be normalized**, or it represents an invalid rotation.
     pub fn from_axis_angle(axis: Vector3<S>, angle: Rad<S>) -> Matrix3<S> {
         let (s, c) = Rad::sin_cos(angle);
         let _1subc = S::one() - c;
@@ -266,6 +268,8 @@ impl<S: BaseFloat> Matrix4<S> {
     }
 
     /// Create a homogeneous transformation matrix from an angle around an arbitrary axis.
+    ///
+    /// The specified axis **must be normalized**, or it represents an invalid rotation.
     pub fn from_axis_angle(axis: Vector3<S>, angle: Rad<S>) -> Matrix4<S> {
         let (s, c) = Rad::sin_cos(angle);
         let _1subc = S::one() - c;
diff --git a/src/rotation.rs b/src/rotation.rs
index d819de0..5352e6e 100644
--- a/src/rotation.rs
+++ b/src/rotation.rs
@@ -72,6 +72,8 @@ pub trait Rotation3<S: BaseFloat>: Rotation<Point3<S>>
                                  + Into<Quaternion<S>>
                                  + From<Euler<Rad<S>>> {
     /// Create a rotation using an angle around a given axis.
+    ///
+    /// The specified axis **must be normalized**, or it represents an invalid rotation.
     fn from_axis_angle(axis: Vector3<S>, angle: Rad<S>) -> Self;
 
     /// Create a rotation from an angle around the `x` axis (pitch).
diff --git a/tests/quaternion.rs b/tests/quaternion.rs
index 10a47af..78ac4f5 100644
--- a/tests/quaternion.rs
+++ b/tests/quaternion.rs
@@ -168,3 +168,55 @@ mod rotate_from_euler {
         assert_approx_eq!(vec3(1.0, 0.0, 0.0), rot * vec);
     }
 }
+
+mod rotate_from_axis_angle {
+    use cgmath::*;
+
+    #[test]
+    fn test_x() {
+        let vec = vec3(0.0, 0.0, 1.0);
+
+        let rot = Quaternion::from_angle_x(deg(90.0).into());
+        assert_approx_eq!(vec3(0.0, -1.0, 0.0), rot * vec);
+    }
+
+    #[test]
+    fn test_y() {
+        let vec = vec3(0.0, 0.0, 1.0);
+
+        let rot = Quaternion::from_angle_y(deg(90.0).into());
+        assert_approx_eq!(vec3(1.0, 0.0, 0.0), rot * vec);
+    }
+
+    #[test]
+    fn test_z() {
+        let vec = vec3(1.0, 0.0, 0.0);
+
+        let rot = Quaternion::from_angle_z(deg(90.0).into());
+        assert_approx_eq!(vec3(0.0, 1.0, 0.0), rot * vec);
+    }
+
+    #[test]
+    fn test_xy() {
+        let vec = vec3(0.0, 0.0, 1.0);
+
+        let rot = Quaternion::from_axis_angle(vec3(1.0, 1.0, 0.0).normalize(), deg(90.0).into());
+        assert_approx_eq!(vec3(2.0f32.sqrt() / 2.0, -2.0f32.sqrt() / 2.0, 0.0), rot * vec);
+    }
+
+    #[test]
+    fn test_yz() {
+        let vec = vec3(1.0, 0.0, 0.0);
+
+        let rot = Quaternion::from_axis_angle(vec3(0.0, 1.0, 1.0).normalize(), deg(-90.0).into());
+        assert_approx_eq!(vec3(0.0, -2.0f32.sqrt() / 2.0, 2.0f32.sqrt() / 2.0), rot * vec);
+    }
+
+    #[test]
+    fn test_xz() {
+        let vec = vec3(0.0, 1.0, 0.0);
+
+        let rot = Quaternion::from_axis_angle(vec3(1.0, 0.0, 1.0).normalize(), deg(90.0).into());
+        assert_approx_eq!(vec3(-2.0f32.sqrt() / 2.0, 0.0, 2.0f32.sqrt() / 2.0), rot * vec);
+    }
+}