Rheumatoid arthritis is associated with both localized and generalized osteoporosis. Localized osteoporosis can be considered to be caused by local disease mechanisms, including the generation of factors from activation of the cytokine pathway. The etiology of generalized osteoporosis has been difficult to elucidate, particularly because of the lack of sensitive techniques to measure bone mineral density. The introduction of single- and dual-photon absorptiometry and quantitative computed tomography has allowed more accurate assessment of bone mineral density. In general, bone mineral density loss at appendicular sites does not correlate well with axial bone density loss. Corticosteroid treatment exaggerates the development of osteoporosis in up to 40% of patients with rheumatoid arthritis. Sex hormone status, physical activity, disease duration, and functional class are all significant predictors for the development of osteoporosis. Current therapy for prevention and treatment is based largely on theoretical considerations. Physical activity should be encouraged once acute joint inflammation has settled. Postmenopausal women and amenorrheic premenopausal women will benefit from cyclical estrogen replacement. Patients with low serum 1,25-dihydroxy vitamin D3 levels, and males with low serum testosterone levels, are candidates for replacement therapy with the appropriate hormones. In patients who are receiving corticosteroids the dose should be limited, and oral calcium supplements are of benefit. The use of the newer corticosteroid deflazacort, and disease-modifying immunosuppressive drugs, are discussed. Other therapeutic options which should be considered, although published trials are scarce, are calcitonin and the diphosphonates. Further studies are awaited concerning the optimum prevention and treatment of osteoporosis associated with rheumatoid arthritis.(ABSTRACT TRUNCATED AT 250 WORDS)