Groups of 30 male and 30 female Sprague-Dawley CD rats, designated as the F0 generation, were exposed to vapor of monochlorobenzene (MCB) at target concentrations of 0, 50, 150, or 450 ppm for 10 weeks prior to mating and during mating, gestation, and lactation. The progeny of the F0 generation was designated as the F1 generation and groups of 30 male and 30 female F1 animals were exposed to the same concentrations of MCB as the F0 parents. Exposure of F1 animals was initiated 1 week postweaning and lasted 11 weeks prior to mating and through mating, gestation, and lactation. All F2 pups were observed through weaning at which time they were killed. Observations made during the study included body weights, food consumption, mating and fertility indices, pup and litter survival indices, and histopathology of selected tissues. No mortality was observed during the course of this study. Body weights and food consumption for all treated groups were comparable to controls during the growth period. Maternal body weight data during gestation and lactation were also comparable between the control and treated groups. Mating and fertility indices for males and females for both generations appeared unaffected by treatment. Pup and litter survival indices for all treated groups were comparable to those of controls. Hepatocellular hypertrophy and renal changes (tubular dilation with eosinophilic material, interstitial nephritis, and foci of regenerative epithelium) were observed among F0 and F1 male rats exposed to 150 and 450 ppm MCB.(ABSTRACT TRUNCATED AT 250 WORDS)