Twenty‐three rheumatic disease patients with glucocorticoid‐induced osteopenia (defined by measurement of forearm bone mass) completed an 18‐month double‐blind, randomized study to assess the effect of oral calcium and 1,25‐dihydroxyvitamin D (1,25‐OH2D) or calcium and placebo on bone and mineral metabolism. Intestinal 47Ca absorption was increased (P < 0.05) and serum parathyroid hormone levels were suppressed (P < 0.01) by 1,25‐OH2D (mean dose 0.4 μg/day); however, no significant gain in forearm bone mass occurred, and bone fractures were frequent in both groups. In the 1,25‐OH2D group, histomorphometric analysis of iliac crest biopsy specimens demonstrated a decrease in osteoclasts/mm2 of trabecular bone (P < 0.05) and parameters of osteoblastic activity (P < 0.05), indicating that 1,25‐OH2D reduced both bone resorption and formation. We conclude that 1,25‐OH2D should not be used for treatment of glucocorticoid‐induced osteopenia. Since patients receiving calcium and placebo did not exhibit a loss of forearm bone mass, elemental calcium supplementation of 500 mg daily might be useful to maintain skeletal mass in patients receiving long‐term glucocorticord therapy.