Osteoporosis is a common adverse reaction induced by glucocorticoid treatment. Bisphosphonate, vitamin D₃ (VD₃) or vitamin K₂ (VK₂) is recommended as first or second choice of drug for treatment of glucocorticoid-induced osteoporosis. In the present study, the treatment effect of risedronate against glucocorticoid-induced osteoporosis in rheumatoid arthritic patients was compared with that of alfacalcidol. Twelve patients were randomized to receive either risedronate (2.5 mg) or alfacalcidol (0.5 μg) daily for 48 weeks. Each patient also received 800 mg of calcium supplementation (800 mg/day) daily. Bone mineral density (BMD) and the biochemical markers of bone turnover were measured before (baseline) and 12, 24, and 48 weeks after treatment with risedronate or alfacalcidol, and the percentage changes in these parameters from baseline were compared.The BMD values 12, 24 and 48 weeks after treatment with risedronate increased by 3.9%, 4.1% and 5.2%, respectively, which were significantly higher than those after treatment with alfacalcidol (2.8%, 2.1% and 2.5%, respectively). Urinary excretion of N-telopeptides of type I collagen and deoxypyridinoline after risedronate treatment were more significantly decreased than that after alfacalcidol treatment. The present findings at least suggest that risedronate is more useful for the prevention and treatment of glucocorticoid-induced osteoporosis in patients with rheumatoid arthritis than alfacalcidol, although the number of patients studied was small.