Tumor necrosis factor (TNF) is an important proinflammatory cytokine that mediates inflammatory synovitis and articular matrix degradation in rheumatoid arthritis (RA). We investigated the ability of adalimumab, a human anti-TNF monoclonal antibody, to inhibit the progression of structural joint damage, reduce the signs and symptoms, and improve physical function in patients with active RA receiving concomitant treatment with methotrexate (MTX).