Axial and appendicular bone mass were studied in 95 patients with rheumatoid arthritis. The aims were to quantify bone mineral density (BMD) and to evaluate the importance of disease activity, duration of disease, functional capacity, and corticosteroid treatment for bone loss in patients with rheumatoid arthritis. The BMD in the lumbar spine (BMDSPINE) did not differ from age-matched healthy controls, but distal forearm BMD (BMDARM) and metacarpal BMD (BMDMCB) were significantly lower in the patients (p < 0.01 and p < 0.001, respectively). Neither BMDSPINE nor BMDMCB were related to the disease activity at the time of investigation. By contrast, BMDARM was decreased in patients with active disease. BMD in any of the three measured locations was not directly correlated to duration of the disease. However, the bone mass in the appendicular skeleton was already decreased within the first two years after the start of the disease. The overall functional capacity in terms of physical activity increased BMD in the axial skeleton. The local functional capacity in terms of grip strength was positively related to BMD in the appendicular skeleton. Patients with severe functional impairment had the lowest BMDARM. The decreased BMD in patients with rheumatoid arthritis seems primarily to be caused by an impaired physical activity which may be related to disease activity. Corticosteroids did not decrease BMD in neither the axial nor the appendicular skeleton. The antiinflammatory effect of steroids lead to clinical improvement, which may counteract the expected negative effect of these drugs on bone in rheumatoid arthritis.