A geometric and kinematic model for describing the global shape and the predominant motions of the human tongue, to be applied in computer animation, is discussed. The model consists of a spatial configuration of moving points that form the vertices of a mesh of 9 3-D triangles. These triangles are interpreted as charge centres (the so-called skeleton) for a potential field, and the surface of the tongue is modelled as an equi-potential surface of this field. In turn, this surface is approximated by a triangular mesh prior to rendering. As to the motion of the skeleton, precautions are taken in order to achieve (approximate) volume conservation; the computation of the triangular mesh describing the surface of the tongue implements penetration avoidance with respect to the palate. Further, the motions of the skeleton derive from a formal speech model which also controls the motion of the lips to arrive at a visually plausible speech synchronous mouth model.