This study will test whether the drug combination of methotrexate and infliximab (anti-TNF-alpha antibody) is more effective than methotrexate alone for treating rheumatoid arthritis early in the disease. (The Food and Drug Administration has approved both treatment regimens for patients with long-standing rheumatoid arthritis.) The study will also evaluate how effectively magnetic resonance imaging (MRI) can detect differences in the development of bone damage in the two treatment groups by as early as 6 months.