The aim of the study was to compare the bone loss and the influence of physical activity between premenopausal women with rheumatoid arthritis (RA) and healthy women. A total of 71 patients with RA and 29 healthy premenopausal women with the criteria of the American College of Rheumatology for RA were followed for 2 years. Of these 85% were Caucasian, aged 38 +/- 6.6 years and with a duration of disease of 88 +/- 50 months and 48 (71.8%) used GC, mean daily dose, 7.3 +/- 3.5 mg. There was a reduction in the T-score of the femoral neck (P = 0.04) and in the Ward region (P = 0.05) in RA. Through logistic regression, it was found that sedentarism was a risk factor for osteopenia in RA, with relative risk of 1.6 (IC = 1.238-1.734). Moderate physical activity reduced the risk of osteopenia by 50%. Sedentarism and low weight are the main factors associated with bone loss. Physical activity reduces bone loss. Early preventive and therapeutic measures must be encouraged.