We present a sketch-based rotation editing system for enriching rotational motion in keyframe animations.Given a set of keyframe orientations of a rigid object,the user first edits its angular velocity trajectory by sketching curves,and then the system computes the altered rotational motion by solving a variational curve fitting problem.The solved rotational motion not only satisfies the orientation constraints at the keyframes,but also fits well the user-specified angular velocity trajectory.Our system is simple and easy to use.We demonstrate its usefulness by adding interesting and realistic rotational details to several keyframe animations.