BACKGROUND: A reliable alternative to steroids for treating polymyalgia rheumatica has not yet been identified. Although infliximab has been used occasionally in steroid-resistant cases, its efficacy has not been demonstrated in a controlled study. OBJECTIVE: To compare the efficacy of prednisone plus infliximab with that of prednisone plus placebo in patients with newly diagnosed polymyalgia rheumatica. DESIGN: Randomized, placebo-controlled trial. SETTING: 7 rheumatology clinics in Italy. PATIENTS: 51 patients with newly diagnosed polymyalgia rheumatica. Patients with associated giant cell arteritis and those who had been previously treated with steroids or biological or immunosuppressive agents were excluded. INTERVENTION: Initial therapy with oral prednisone tapered from 15 mg/d to 0 mg/d over 16 weeks according to a standard protocol, plus infusions of placebo or infliximab, 3 mg/kg of body weight, at weeks 0, 2, 6, 14, and 22. MEASUREMENTS: The primary efficacy end point was the proportion of patients without relapse or recurrence through week 52. Secondary outcomes were the proportion of patients no longer taking prednisone, the number of relapses and recurrences, the duration of prednisone therapy, and the cumulative prednisone dose. RESULTS: Four patients (3 in the infliximab group and 1 in the placebo group) did not complete the trial. The proportion of patients who were free of relapse and recurrence at 52 weeks did not differ between groups (6 of 20 patients [30%] in the infliximab group vs. 10 of 27 patients [37%] in the placebo group; adjusted risk difference, -3 percentage points [95% CI, -31 to 24 percentage points]; P = 0.80). In a sensitivity analysis that included dropouts, the best-case scenario yielded a difference of 5 percentage points (CI, -21 to 31 percentage points) between the groups. The secondary outcomes at weeks 22 and 52 did not differ between the groups. LIMITATIONS: The study had a small sample and a short follow-up. A low dosage of infliximab was used, and the prednisone dosage was rapidly tapered. CONCLUSIONS: Although too small to be definitive, the trial provides evidence that adding infliximab to prednisone for treating newly diagnosed polymyalgia rheumatica is of no benefit and may be harmful. If there is benefit, it is unlikely to be large. Australian Clinical Trials Registry number: ACTRN012606000205538.