['Total hip replacement (THR) outcomes have been worse for patients with rheumatoid arthritis (RA) compared with those who have osteoarthritis (OA). Whether this remains true in contemporary patients with RA with a high use of disease-modifying and biologic therapy is unknown. The purpose of our study is to assess pain, function, and quality of life 2 years after primary THR, comparing patients with RA and patients with OA.', 'Baseline and 2-year data were compared between validated patients with RA and patients with OA who were enrolled in a single-center THR registry between May 1, 2007, and February 25, 2011.', 'There were 5666 eligible primary THR identified, of which 193 were for RA. RA THR had worse baseline Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain (44.8 vs 53.2, p < 0.001) and function (38.7 vs 49.9, p < 0.001) compared with OA. These differences remained after surgery: pain (88.4 vs 94.0, p < 0.001) and function (82.9 vs 91.8, p < 0.001). Patients with RA were as likely to have a significant improvement as patients with OA (Δ WOMAC > 10) in pain (94% vs 96%, p = 0.35) and function (95% vs 94%, p = 0.69), but were 4 times as likely to have worse function (WOMAC ≤ 60; 19% vs 4%, p < 0.001) and pain (12% vs 3%, p < 0.001). In multivariate logistic regression controlling for multiple potential confounders, RA increased the odds of poor postoperative function (OR 4.32, 95% CI 1.57-11.9), and in patients without a previous primary THR, worse postoperative pain (OR 3.17, 95% CI 1.06-9.53).'] Are patients with rheumatoid arthritis more likely to have pain and poor function after total hip replacements than patients with osteoarthritis?