The toxicity of chlorinated organic compounds which may be generated as a by-product of drinking water chlorination has been an issue of increasing concern. Relatively few data are available concerning their reproductive toxicity. The present study was designed to evaluate the reproductive effects of one of these compounds, 2,4,6-trichlorophenol (TCP) in male and female rats. Adult males were treated with either 0, 100, 500, or 1000 mg/kg of TCP (p.o.) for 10 weeks at which time semen evaluations were conducted on ejaculates recovered from the genital tract of receptive females. Fertility was assessed in the 0 and 1000 mg/kg groups. Females were treated with identical doses for two weeks prior to pregnancy then throughout gestation. Dams were allowed to litter and pup development was monitored until Day 42 post-partum. TCP had no effect on any sperm parameter or male fertility. Treatment of females with 1000 mg/kg of TCP produced gross maternal toxicity as reflected in increased lethality and decreased weight gains in the dams.