The need to visualize and interpret human body movement data from experiments and simulations has led to the development of a new three-dimensional representation for the human body. Based on a skeleton of joints and segments, the model is manipulated by specifying joint positions with respect to arbitrary frames of reference. The external form is modelled as the union of overlapping spheres which define the surface of each segment. The properties of the segment and sphere model include: an ability to utilize any connected portion of the body in order to examine selected movements without computing movements of undesired parts, a naming mechanism for describing parts within a segment, and a collision detection algorithm for finding contacts or illegal intersections of the body with itself or other objects. Several display algorithms are possible, including inexpensive hidden surface removal. The spherical body model can also be easily combined with planar polygon object environments.