One three-day course of intravenous pamidronate sodium (3-amino-1-hydroxypropylidene-1,1-bisphosphonate), 30 mg/d, in a patient with calcitonin-resistant Paget's disease resulted in the following: marked clinical improvement within two weeks; normalization of urinary hydroxyproline value; fall of serum alkaline phosphatase value (900 to 250 U/L); a rise in serum osteocalcin value by the tenth week that returned to pretreatment levels in the 16th week; transient hypocalcemia with elevation of parathyroid hormone value; reduction in urinary calcium excretion; and improvement in bone scans. No adverse reactions occurred, with the exception of mild and transient hyperpyrexia for 48 hours during pamidronate administration. White blood cell counts did not change and serum interleukin 1 was undetectable before and after treatment with pamidronate. Pamidronate seems to be highly effective in the treatment of Paget's disease of the bone, but its profound effects on mineral and bone metabolism require close monitoring during the short-term period of intravenous treatment.