A prospective, multicenter, randomized trial comparing pamidronate administration (60-90 mg once a month for 1 year) versus simple observation in 177 patients with asymptomatic myeloma was performed to explore whether the administration of this drug reduces the rate of and/or the time to progression to overt, symptomatic disease. No relevant side effects were recorded in pamidronate-treated patients. With a minimum follow-up of 5 years for live patients, there were 56/89 (62.9%) progressions in the pamidronate-treated group and 55/88 (62.5%) within the controls (p = NS). Median time to progression was 46 and 48 months, respectively (p = NS). Overall survival was also similar between the two groups. Skeletal-related events at the time of progression were observed in 40/55 (72.7%) controls, but only in 22/56 (39.2%) pamidronate-treated patients (p = 0.009). In conclusion, the administration of pamidronate in asymptomatic myeloma, while reducing bone involvement at progression, did not decrease the risk of transformation and the time to progression into overt myeloma.