Percutaneous reduction of cyst volume was performed in 10 patients with autosomal dominant polycystic kidney disease and its effects on renal function were studied. Although creatinine clearance, urinary excretion of beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase, and renal uptake of 99mtechnetium-dimercaptosuccinic acid did not change significantly, a transient increase in urinary protein and a decrease in inulin clearance were observed. Complications, such as hematuria, fever and decreases in hematocrit, were slight and transient in most patients. This procedure holds little promise for altering the course of polycystic kidney disease.