Measurements of functional performance were compared before and at 6 months after 58 McKee-Farrar, 50 Charnley, and 57 Muller total hip replacements in 143 patients. The measurment included: range of motion of the hip, hip abductor and adductor-muscle torque, weight-bearing activity during standing, forces applied to canes or crutches, and multiple components of walking performance. Each group of patients improved significantly after surgery in all of the components measured. Early postoperative differences among the 3 groups were found with respect to pain ratings, impressions of hip status, hip motions, muscle torque, the number of patients using assistive devices, and certain components of walking performance. There is nothing to suggest that the performance of any 1 group is distinctly better or worse than that of any other group 6 months after surgery. On the basis of average values, each group improved in every component of function and it is gratifying that, except for a few patients who developed postoperative infection, each patient could be considered to have successful reconstruction.