A new approach to the study of 'programmed' human locomotion is made using the methods of optimal programming and modern control theory. Development of the problem structure relies closely on the phasic and temporal characteristics of the biped gait. The result is a multi-arc programming problem with three stages. Each stage involves appropriate dynamic constraints which reflect the particular nature of the phasic activity. joining of the arcs is arranged in such a way as to maintain continuity of certain trajectories as well as repeatability of motion. A novelty of the approach is that the theory could be used to study walking behavior under different environmental conditions, such as walking up-stairs or over a hole. A distinct feature of the present approach which differs from other studies is the presence of a minimizing performance criterion. Based on external characteristics of muscles and certain assumptions regarding normal locomotion, a simple quadratic type of criterion is proposed. This performance criterion is meaningful in that it is shown to be proportional to the mechanical work done during normal walking. Invoking the necessary conditions of optimal control theory, a multi-point boundary value problem is obtained. A penalty function technique is employed for iterative numerical solution.