We evaluated low-dose calcitriol (0.25 microgram b.i.d.) in combination with 1 g of supplemental calcium therapy as treatment for osteopenic women over 60 years of age (n = 4). Control patients (n = 6) received ergocalciferol (50,000 units twice a week) and 1 g of supplemental calcium. Bone biopsies and CT-determined bone mineral density were done initially and after 1 year of therapy. Bone mineral density increased from 77 +/- 18 to 88 +/- 9 mg/ml (NS) in the calcitriol-treated group and from 87 +/- 13 to 112 +/- 30 mg/ml (NS) in the ergocalciferol-treated group. There was also no significant change in bone volume, as determined by bone biopsy in either group. No compression fractures occurred in either treatment group. After 1 year of therapy, urinary calcium excretion was increased significantly above that observed in age-matched untreated women. Creatinine clearance did not change significantly. Hypercalcemia was rare. In summary, we found calcitriol was not superior to ergocalciferol in preventing progressive bone loss and fractures. Both therapies were associated with significant hypercalciuria.