This paper describes a simple modelling technique enabling parametric analysis of femoral prosthetic design. Model femora cast in rigid polyurethane foam and prosthetic models made from various plastics are used to simulate prosthetic implants and natural bone. The model prostheses were matched to the model femora on the basis of flexural stiffness. The results of tests using a constant stem design made from two different simulated materials, namely titanium and chrome cobalt are presented. Two loading configurations were examined; one with the femur in a neutral orientation and the other with the femur in flexion and abduction. The influence of a collar to load the femoral neck was also investigated. The more flexible prostheses, simulating titanium, offer significant advantages. Stem stresses are lower and the femur is loaded more physiologically then with the more rigid chrome cobalt model prostheses. The study emphasises the importance of considering anteroposterior load in the design of femoral implants.