High-energy shock waves were used to disintegrate kidney stones in dogs and man. In 96% of 60 dogs with surgically implanted renal pelvic stones, the fragments were discharged in the urine. The same effect was achieved in 20 out of 21 patients with renal pelvic stones. In the twenty-first patient, a staghorn calculus was broken up to facilitate surgical removal. 2 patients with upper ureteric stones also received shock waves, but their stones had to be removed surgically; in 1 of these the stone had been embedded in the ureteric wall by connective tissue. The procedure can in many cases be done under epidural instead of general anaesthesia. Side-effects consisted of slight haematuria and, occasionally, of easily treatable ureteric colic. They were probably due to passage of fragments down the ureter. Disintergration of kidney stones by shock waves seems to be a promising form of treatment that reduces the need for surgery.