Three-dimensional finite-element stress analyses were used to compare the fixation of six tibial component configurations of surface-replacement-type total knee prostheses, based on the stresses in the cancellous bone, in the polymethylmethacrylate, and at the bone cement-bone interface. The results indicate that, in general, metal components provide lower system stresses than polyethylene components, particularly in the methacrylate and the cancellous bone, and that one-piece designs give lower bone cement-bone interface stresses compared with those with separated condylar components. Of the designs considered, a single-post, metal-backed design provided the lowest system stresses over-all. A great and confusing variety of tibial component designs exists today, with more in the process of development. Short of long-term clinical trials, there are few objective methods by which these designs can be evaluated and long-term performance predicted. There is evidence from clinical results that excessively high stresses in the system can lead to loosening of the tibial component. The finite-element method provides a method for comparing prosthetic designs using system stresses as a design criterion. On this basis, we analyzed the stress distributions for several types of tibial components and discuss the advantages and disadvantages of their designs.