In an effort to identify the role of extracorporeal shock-wave lithotripsy (ESWL) in the treatment of patients with medullary sponge kidney, a retrospective review of our experience with the Dornier HM-3 lithotriptor is presented. From 1986-1991 17 patients with medullary sponge kidney ranging in age from twenty-eight to fifty-eight years received 31 treatments to a total of 24 renal units. Follow-up ranged from four to fifty-six months with an average follow-up of twenty-five months. ESWL appears to have a role in the treatment of symptomatic urolithiasis in patients with medullary sponge kidney. There may also be some benefit in treating parenchymal calcifications. No significant side effects from the treatment were noted.