Commonly used total hip arthroplasty scores take into account pain, function, walking, and range of motion. The purpose of this study was to evaluate the value of patient activity level as part of the outcome of total hip arthroplasty. Using linear regression analysis, the relationship between patient activity level (University of California Los Angeles activity score), the Harris Hip Score, and the Short Form-12 health survey was evaluated in 152 patients (mean age, 58.7 years) with a mean follow-up 5.2 years (range, 2-21 years). The University of California Los Angeles activity scale had an R(2) value of 0.39 and 0.19 to the Short Form-12 physical and mental components, respectively, and 0.32 to the Harris Hip Score. By evaluating patient activity level, one obtains important qualitative information in assessing the clinical outcome after total hip arthroplasty.