Effect of selenium pretreatment (0.2 mg/kg/day, as sodium selenite), 4 h prior to mercury treatment (0.4 mg/kg/day, as mercuric chloride), administered intraperitoneally, was examined after daily exposure for 20 days' in rats. Liver, kidney and brain tissues were assayed for malondialdehyde (MDA) level, glutathione (GSH) content and mercury concentration. Mercury induced MDA levels, which was also observed in selenium pretreated animals. Significant reduction in GSH levels was observed in mercury alone and selenium pretreated animals. Mercury accumulation was in the order of kidney, liver and brain. Selenium pretreatment resulted in further enhancement in mercury accumulation in liver and kidney.