The authors conducted this study to determine if very-low-dose (i.e., 4 ppm) mercury is nephrotoxic and, if so, whether the nephrotoxic actions of mercury in mice could be prevented by zinc intake. Animals were administered 4 ppm mercuric chloride and/or 800 ppm zinc chloride in their drinking water for 12 wk. The animals were sacrificed at the end of the exposure period, and their kidneys were excised, weighed, and processed for histological study. Both metals reduced significantly (p < .05) the absolute and relative kidney weights of the animals. Zinc-treated animals showed normal kidney histology that was comparable with that of the control. Mercury treatment produced necrosis and widening of the glomeruli, whereas a combination of both metals resulted in protection from the toxic effects, with most nephrons resembling the control. The results indicate that low-dose mercury exposure in mice kidney induces some degenerative effects, which are prevented by zinc.