Sixty-two steroid-dependent asthmatics who had not received any form of treatment to prevent bone loss were studied during a 12-month period. Patients were randomly divided into two groups. Thirty-one patients were treated with 1 g of elemental calcium taken daily plus 100 IU of salmon calcitonin every other day, administered subcutaneously; the remaining 31 patients received only calcium supplementation. In the calcitonin group, 11 patients dropped out of the study because of severe side effects (seven patients), lack of compliance (three patients), and exacerbation of asthma (one patient). The 20 patients who completed the 12-month follow-up period were analyzed and compared with 20 sex-matched patients from the control group. At one year, bone mineral density (BMD) had increased in the calcitonin group by a mean of 4% (p less than or equal to 0.001), whereas in the control group BMD had decreased by 2.5% (p less than or equal to 0.05). Parameters of bone remodeling (alkaline phosphatase and osteocalcin) decreased significantly in the calcitonin-treated group but not in the control group. Our findings show that calcitonin 100 IU, given three times/wk, is an effective drug in the treatment of steroid-induced osteopenia. Side effects, however, are frequent and cause a high degree of dropout from therapy. These findings suggest that further studies should be carried out with lower doses of calcitonin or by other better tolerated forms of delivery such as in a nasal spray.