Paget's disease of bone is characterized by primary osteoclastic dysfunction and prolonged treatment with conventional medications including calcitonin and etidronate, results in a number of patients becoming refractory to treatment. We have evaluated the effectiveness of three dosage regimes of aminohydroxypropylidene bisphosphonate (pamidronate) in 15 patients with extensive Paget's disease who had become refractory to conventional therapy. Nine patients had pamidronate (intravenous infusion of 30 mg over 4-5 hours at monthly intervals) for 6 months. A further four patients received 30 mg of pamidronate infusion daily for 6 consecutive days and another two patients, 60 mg on 3 consecutive days (total dose of 180 mg/patient). In all three groups the bone-specific alkaline phosphatase and urinary hydroxyproline excretion both fell by 75% (P < 0.001). All but one patient showed a marked improvement in clinical symptomatology (pain and mobility) and biochemical parameters indicating decreased bone turnover. Remissions achieved (> 12 months) with all three regimens were comparable. The pagetic bone pain was reduced and the mobility was significantly improved after 3 months of therapy and was continued for up to 1 year. Currently, it may be difficult to justify the use of intravenous bisphosphonate as the first line of therapy for Paget's disease, but it does seem to have a definite place in patients with severe Paget's disease who do not respond to other therapeutic agents. Here we demonstrate that pamidronate is highly effective in patients with extensive Paget's disease who became refractory to conventional treatment. Further studies are necessary to optimize the dosage and frequency of administration of pamidronate.