Spherical linear interpolation has got a number of important applications in computer graphics. We show how spherical interpolation can be performed efficiently even for the case when the angle vary quadratically over the interval. The computation will be fast since the implementation does not need to evaluate any trigonometric functions in the inner loop. Furthermore; no renormalization is necessary and therefore it is a true spherical interpolation. This type of interpolation; with non equal angle steps; should be useful for animation with accelerating or decelerating movements; or perhaps even in other types of applications.