The aim of the study was to assess risedronate's effect on bone mineral density in postmenopausal women with rheumatoid arthritis receiving glucocorticoids. We carried out a two center, 2 year, double-masked, placebo-controlled trial with a third year of nontreatment follow-up. We studied 120 women requiring long-term glucocorticoid therapy at > 2.5 mg/day prednisolone randomized to treatment with daily placebo; daily 2.5 mg risedronate; or cyclical 15 mg risedronate (2 out of 12 weeks). At 97 weeks, bone mineral density was maintained at the lumbar spine (+1.4%) and trochanter (+0.4%) in the daily 2.5 mg risedronate group, while significant bone loss occurred in the placebo group (-1.6%, p = 0.03; and 4.0%, p < 0.005, respectively). At the femoral neck, there was a nonsignificant bone loss in the daily 2.5 mg risedronate group (-1.0%) while in the placebo group bone mass decreased significantly (-3.6%, p < 0.001). The difference between placebo and daily 2.5 mg risedronate groups was significant at the lumbar spine (p = 0.009) and trochanter (p = 0.02) but did not reach statistical significance at the femoral neck. Although not significantly different from placebo at the lumbar spine, the overall effect of the cyclical regimen was similar to that of the daily 2.5 mg risedronate regimen. Treatment withdrawal led to bone loss in the risedronate groups that was significant at the lumbar spine. A similar number of patients experienced adverse events (including upper gastrointestinal events) across treatment groups and risedronate was generally well tolerated. Thus risedronate preserves bone mass in postmenopausal women with rheumatoid arthritis receiving glucocorticoids while patients receiving a placebo have significant bone loss.