An investigation was carried out into renal injury caused by extracorporeal piezoelectric lithotripsy (EPL) using an EDAP lithotriptor. Four urinary proteins, with a molecular weight range of 160000-14500, immunoglobulin G (IgG), N-acetyl-beta-glucosaminidase (NAG), albumin and lysozyme, were monitored in 27 patients 1 day before and 1, 7, 30, 90 and 180 days after unilateral EPL treatment. All patients had non-obstructive renal stones, previously untreated. Apart from 5 patients with stablised hypertension and 6 with persistent urinary infections due to the infected stones, all patients appeared healthy, as confirmed by clinical, haematological and biochemical investigations. Only albumin levels increased significantly 1 day after treatment; statistically nonsignificant increases and decreases were recorded in the levels of NAG and lysozome respectively. IgG was beyond the limit of detection (less than 0.5 mg%) in all patients. The albumin level returned to normal 7 days after treatment. The EPL-induced increase in albumin was recorded in 88% of patients, compared with increased levels of NAG in 46% and lysozyme in 64%, mainly in those with infected stones. These findings indicated a transient glomerular injury after EPL treatment.