Summary: This paper describes an algorithm for automatically generating a control skeleton (sometimes called an IK skeleton) for use in animating a polygonal data model. The algorithm consists of several steps, each of which is performed automatically. The basic process involves discretizing the figure, computing its discrete medial surface (DMS), and then using the DMS both to create the skeletal structure and to attach the vertices of the model to that structure. The system can produce a reasonably good control skeleton for any of a variety of figures in as little as 1 or 2 min on a low-end PC.