OBJECTIVE The beneficial effect of oestrogens on bone mineral density in women with osteoporosis is well known. Patients with rheumatoid arthritis (RA) are at risk for osteoporosis. A study was therefore set up to investigate the effects of adjuvant oestrogen treatment on bone metabolism and bone mineral density in postmenopausal women with RA. METHODS Forty postmenopausal women with active RA were admitted to a placebo controlled, double blind study investigating the beneficial effect of adjuvant oestradiols or placebo on bone metabolism and bone mineral density. Thirty three patients completed 52 weeks of treatment. RESULTS At the start both treatment groups were comparable for all parameters. In the oestrogen group serum concentrations of osteocalcin decreased and concentrations of sex hormone binding globulin increased during the study. Bone mineral density measured by dual energy x ray absorptiometry increased significantly in the lumbar vertebral spine and femoral neck in the oestrogen group compared with the placebo group. CONCLUSIONS This study shows that the use of adjuvant oestrogens in post-menopausal women with active RA increases bone mineral density.