Mercuric chloride (HgCl2)-induced nephrotoxicity, as measured by functional and biochemical parameters was evaluated in rats at different kidney non-protein sulfhydryls (NPS) levels. Diethylmaleate (DEM) induced a 75% of NPS diminution 1 h after the administration. Renal function (clearance) and biochemical measurements (gamma-glutamyltranspeptidase activity in urine, and lipoperoxides in kidney tissue) were impaired when the animals were HgCl2-treated. Values were highly impaired when the kidneys were NPS-depleted and were improved when NPS pools were previously increased although they were not similar to control values. DEM treatment promoted a higher accumulation of HgCl2 in both kidney and liver while NAC-treatment reduced significantly the metal content in these organs. These data are in favour of a positive relationship among mercury content and organ injury. On the other hand, mercury content increased while NPS levels diminished. NPS might play a role in the HgCl2 detoxification and thus avoids mercury accumulation and mercury effects.