Data on the long-term treatment of myeloma bone disease with bisphosphonates are scanty. In a prospective pilot trial we evaluated the effect of long-term parenteral administration of dichloromethylene bisphosphonate (Clodronate), in addition to standard chemotherapy, in 30 patients with active myeloma bone disease. Patients were treated with a mean of 4 courses (range 2-8) of Clodronate: 300 mg/day i.v. for seven days followed by 100 mg/day i.m. for 10 days, administered at a mean interval of 4 months (range 3-6). The median follow-up was 24 months (range 8-36). Clodronate reduced bone pain rapidly and significantly, and reduced the mean values of the biochemical indices of bone resorption to within normal limits; these effects were maintained throughout the follow-up. In three hypercalcemic episodes serum calcium became normal after 2-5 days of treatment with Clodronate. No toxic or side effects were noticed. The occurrence of skeletal morbidity in patients treated with Clodronate was compared with that observed in the control group of myeloma patients (p less than 0.001) in severe bone pain as well as in the incidence of new osteolytic lesions and pathological fractures (p less than 0.001). Supportive Clodronate therapy contributes significantly in controlling the progression of myeloma bone disease.