This work investigated the preventive effects of ZnCl(2) on renal and hepatic alterations induced by HgCl(2) in young rats. Wistar rats of 3 days old were treated (s.c.) on consecutive days with saline or ZnCl(2) 27 mg/kg/day from the 3rd to the 7th and with saline or HgCl(2) 5.0mg/kg/day from the 8th to the 12th day of life. Pups were sacrificed 24h after the last dose and samples were collected. The creatinine and urea dosages, used as renal parameters, presented increases of 35% and 500%, respectively. The alanine aminotransferase and lactic dehydrogenase activities, used as hepatic parameters, presented a decrease (40%) and no alteration, respectively, by mercury exposure. The glycemia was diminished and the hepatic glycogen was not modified by mercury. All the mercury effects were prevented by zinc. These results suggest that mercury intoxication of young rats alters the renal function but does not modify the hepatic parameters, and previous exposure to zinc is able to avoid the renal damage.