Effects of mercuric chloride (MC) on the reproductive performance of two successive generations of rats was evaluated. F(0) rats were exposed to 0.0:0.0 (males:females), 0.50:0.75 (males:females), 1.00:1.50 (males:females) and 1.50:2.50 (males:females) mg/kg/day MC. Selected parental F(1) males and females were exposed to the same doses received by their parents (F(0)). Significant differences resulting from exposure of the F(0) generation to MC were found in implantation efficiency, fertility, live births and day 4 survival indices, litter size, and the body weight of F(1) pups. However, the continued exposure of the F(1) generation to MC did not affect fertility index or litter size, but did significantly affect implantation efficiency, live births and day 4 survival indices. In F(0) males, body weight and weights of the kidneys, testes, epididymides, prostate and seminal vesicles were significantly different, while in F(1) males, body weight, kidney weight, brain weight, liver weight and the weights of the testes, prostate and seminal vesicles were significantly different. In F(0) females, body weight and the weights of the kidneys, brain and liver were significantly different, while in F(1,) females, body weight, as well as the weights of the kidneys, liver, adrenals, uterus and ovaries were significantly different. These data showed that exposure to MC resulted in more adverse reproductive effects in the first generation and that these effects moderated in the second generation.