A two-dimensional stress analysis was used to study the effects of some of the factors leading to early fatigue failure of the femoral stem in total hip prostheses. The results show that loss of proximal stem support at the level of the calcar femorale will result in stem stress levels which can lead to fatigue failure. In addition, the role of body weight and range of cyclic stress fluctuation play an important role in fatigue life under conditions where the stem has lost proximal support. These results indicate that stem design could be improved by incorporating some means of ensuring adequate support at the calcar femoralre maximum tensile stresses are found to occur.