The effects of inhaled epichlorohydrin (ECH) on the fertility of Sprague-Dawley rats and New Zealand white rabbits were studied. Groups of 10 male rabbits, 30 male rats, and 30 female rats were exposed to 0, 5, 25, or 50 ppm of ECH vapor for 6 hr/day, 5 days/week for 10 weeks, and were held for a 10-week postexposure females. Exposed male rats were mated with unexposed females at several intervals during and after the exposure period. In addition, female rats which had been exposed for the 10-week period were mated with unexposed males and allowed to deliver their young. Exposure to 50 ppm of ECH vapor for 10 weeks resulted in transient infertility in the male Sprague-Dawley rats; recovery of fertility in rats occurred during the second week after termination of exposure. Male rats exposed to 25 ppm of ECH were able to impregnate unexposed females; however, fewer implantations were observed in these females than in the females mated to control males suggesting that fertility was adversely affected in this group as well. This effect also was reversed by the second week following termination of exposure. The incidence of resorptions in the unexposed female rats which were bred to the exposed males was not adversely affected. Among female rats exposed to ECH, no adverse effects were observed on estrus cycle, pregnancy rate, parturition, or the number and viability of the offspring. No discernible effects were noted on the volume of the ejaculate or on the motility, viability, concentration, or fertility of spermatozoa from male rabbits exposed to up to 50 ppm of ECH. Histologic examination of tissues from an interim and final termination of the exposed animals indicated that the most severely affected organ following inhalation exposure to 25 or 50 ppm of epichlorohydrin in both rats and rabbits was the nasal turbinates. These lesions, interpreted to be a result of irritation from the test material, were no longer present in animals which were held for the 10-week postexposure period. No adverse effects were observed among rats or rabbits exposed to 5 ppm of ECH for 10 weeks.