A canine total hip arthroplasty model was used to examine micromotion and bone apposition to a proximally two-thirds madreporic-surfaced femoral prosthesis. Micromotion was also measured following initial press-fit implantation into canine cadaveric femora. After initial press-fit fixation and either 6 or 24 months of biologic fixation, micromotion was less than 23 microns in the proximal and midstem regions, a magnitude consistent with bone apposition. Bone apposition was greatest near the junction of the madreporic and smooth surfaces and was not significantly different between 6 and 24 months (51% at 6 months and 47% at 24 months). The quality of the interface tissue appears to be conductive to long-term fixation.