Repeated exposure of adult female Wistar rats to 3-methylcholanthrene (MC) (25 mg kg(-1) b.w., i.p., 2xwk, 1 mo) was associated with a significant increase in estrus cycle length. In addition, an increased frequency of females with constant diestrus and abnormal cycles was observed. Young females which had been exposed to MC prepubertally or whose parents had been treated with MC before and during mating also demonstrated cycle prolongation and an increased incidence of constant diestrus and abnormal cycles. These changes in female reproductive function were not associated with measurable changes in plasma sex hormone levels. In contrast, MC exposure in adult males was associated with significant reductions in circulating plasma testosterone levels. The present data also suggest that the offspring of parents who had been exposed repeatedly to MC before and during mating are also affected. Although the central nervous system in offspring of MC-treated parents appeared to be intact, their oral body temperature was significantly lower.