This paper describes the control of a simulated three-dimensional model of a human runner. The rigid body model has seventeen segments and thirty controlled degrees of freedom. The dynamic parameters of the simulation were computed using data measured from humans to produce a model that is biomechanically realistic within the constraints of a rigid body approximation. We developed locomotion control algorithms that allow the model to run at a variety of speeds and to turn to face in an arbitrary direction on the plane. The realism of the simulation is evaluaeted by competing the computed motion to that of humans performing similar maneuvers. We perform the comparison quantitatively with real video images and quantitatively with biomechanical data.