This 3 arm study assessed the efficacy of rituximab (MabThera®/Rituxan®) in the prevention of progression of structural joint damage in participants with active rheumatoid arthritis who had an inadequate clinical response to methotrexate. Participants were randomized to receive rituximab 500 mg intravenously (iv), rituximab 1000 mg iv, or placebo iv on days 1 and 15 every 24 weeks in the main study; all participants received concomitant methotrexate at a stable dose of 12.5-25 mg/week throughout the study. Further courses of rituximab were provided to eligible participants. Structural joint damage was assessed by magnetic resonance imaging (MRI) at baseline and at intervals during the study.