Our aim was to evaluate the effects of the potent endogenous free radical scavenger melatonin on extracorporeal-shock-wave lithotripsy (ESWL) induced renal impairment. The study was performed using 30 rabbits which were divided into two groups. Both groups were exposed to 3,000 shock waves at 18 Kv. The animals in the first group were treated with melatonin for 8 days. Controls and melatonin treated rabbits were killed a week after ESWL. MDA, uric acid and white cell counts were used as markers of oxidative stress. The mean levels of uric acid and white cell counts were significantly lower in the melatonin treated group than in the controls. The mean level of MDA was also significantly lower in the melatonin treated group compared to the controls. Our results show that melatonin may exhibit a protective effect on free radical mediated oxidative damage induced by ESWL in rabbit kidney.