Bisphosphonates inhibit osteoclastic bone destruction that may be stimulated by myeloma cells. By this way, bisphosphonates carry the potential to lower the number of new pathological fractures, of hypercalcaemic events, and of intensity of bone pain as was published earlier. Clodronate has been administered orally in most clinical studies so far despite of its poor bioavailability from the gastrointestinal tract. The aim of our study was to evaluate bone mineral density (BMD) changes in 34 newly diagnosed multiple myeloma patients regularly treated by 900 mg of clodronate in slow intravenous infusions on an outpatient basis in two-week intervals for at least 24 months. BMD was evaluated by CT scanning every six months. Initial values of trabecular BMD were only about 60 per cent of age- and sex-adjusted healthy population values. Clodronate therapy seemed to preserve BMD within the period of two or three years. This effect was seen not only in patients responding to chemotherapy but even in the small subgroup of patients with persisting active disease. We conclude that the long-term intravenous clodronate therapy may contribute to the preservation of BMD and thus calcium hydroxyapatite in bones in multiple myeloma patients concomitantly treated by chemotherapy. The administration of clodronate should start early in the course of disease, before BMD has been markedly reduced.