Collision and interference detection among 3-D moving objects is an important issue in the simulation of their behavior. This paper presents a new model for representing 3-D objects and a corresponding effective algorithm for detecting collisions and interferences among moving objects. Objects can be represented for efficient collision and interference detection by a hierarchy of oct - sphere model (HOSM). Algorithms are given for building the HOSM and for detecting collisions and interferences between moving objects. On the basis of HOSM, the algorithm checks only intersections between the nodes of the models which are on the surfaces of the objects. Furthermore, because a node of HOSM represents a spherical region, the collision between the two nodes can be easily found just by calculating the distance between the centers of the two spheres corresponding to them no matter how the objects move. Finally, we discuss the efficiency of the algorithm through an example.