Mechanical stresses are widely assumed to influence the form and structure of bone. The implantation of prosthetic components into trabecular bone are also assumed to alter the stresses in the surrounding trabeculae and these altered stresses are often implicated in the pathogenesis of component loosening. The objective of this investigation was to examine the stress-morphology relationships for trabecular bone around implants for which there was a controlled and predictable alteration in the stress fields. For this purpose two different experimental models were developed using geometrically simplified implants of various materials and surface conditions. Cobalt chromium cylinders with a sintered-bead porous coating were implanted unilaterally into ovine calcanei and stainless steel spheres with either a polished surface or a sintered-bead porous coating were implanted unilaterally into equine patellae. The animals were maintained for periods of 10 to 24 weeks. Stereologic methods were then used to quantify the morphology of the trabecular bone in the experimental specimens and in the untreated contralateral controls. Structural analyses were performed using the displacement-based finite element method to predict the stresses surrounding the implants. The finite element models were validated by comparing the principal stress directions with the material orientation in the control specimens. This assumes that the trabecular architecture was aligned with the principal stress directions in accordance with the trajectorial theory of bone architecture 2 A linear regression for the control equine patellae yielded an R = 0.87. The remodeling response was then evaluated by comparing the stresses and trabecular alignment around the implants in the experimental specimens. 2 A linear regression for the experimental equine patellae yielded an R = 0.89. The two models were distinguished by the high degree of trabecular orientation in the ovine calcanei as opposed to the more isotropic architecture of the equine patellae. As a consequence, the changes induced in the trabecular orientation were greater in the equine patellae. In general, the remodeling response around the smooth implants was greater than that around those porous implants which exhibited bone ingrowth. In accordance with these differences, the finite element models predicted greater changes in the stresses adjacent to the smooth implants due to the nonlinear boundary conditions. However, it did not appear that the trajectorial theory, in its simplest form, was applicable to the remodeling induced by the implants. In both models, the trabeculae were most often aligned with the stress component of the greatest magnitude. However, in the equine models, the alignment was better in regions where tension predominated. In some regions were compression predominated, the principal material direction was 90 to the direction of principal compression. This suggests that cross struts may be formed to resist buckling of the trabeculae under compression. The equine models also demonstrated that, under certain circumstances, small changes in the stress state may result in large changes in the principal material orientation. In contrast, in the ovine models, the highly oriented trabeculae were more often aligned with the direction of principal compression. The stress changes induced by the ingrown porous implants were insufficient to induce significant changes in the trabecular orientation. Both models demonstrated a linear relationship between the change in bone areal density and the change in von Mises effective stress.