Groups of 10 male New Zealand white rabbits were exposed by inhalation to 0, 0.1, 1.0 or 10 ppm of 1,2-dibromo-3-chloropropane (DBCP) vapor for 6 hours/day, 5 days/week for 14 weeks, except that the 10 ppm group was exposed for only 8 weeks due to mortality. The semen of rabbits was evaluated on a weekly basis during the exposure period and at periodic intervals during a recovery period (32 weeks for all groups except the 10 ppm groups which was for 38 weeks). In order to assess the fertility of the exposed rabbits, each male was allowed to mate with an unexposed female at the 14th and 41st week of the study. Exposure of rabbits to 1 and 10 ppm of DBCP by inhalation produced adverse reproductive effects as well as decreases in sperm count, motility and viability. Rabbits treated at 1 and 10 ppm had decreased sperm counts between the 8th and 14th weeks of the study. All of the 10 ppm rabbits were infertile when mated during the 14th week. The effects of DBCP on spermatogenesis were shown to be essentially reversible in rabbits exposed to 1 ppm; however, at 10 ppm, recovery was not complete under the conditions of the test. Rabbits exposed to 10 ppm had severe testicular alterations as early as 4 weeks into the study and these progressed to severe testicular atrophy by 8 weeks. Those exposed to 1 ppm for 14 weeks developed moderate testicular atrophy (approximately 50% reduction in size). Following the recovery period, the rabbits in the 10 ppm group had evidence of partial reversibility of the testicular atrophy. Electron microscopic evaluation of testicular tissue confirmed findings by light microscopy effects and also indicated increased numbers of abnormal sperm within the seminiferous tubules of rabbits at both the 10 and 1 ppm exposure levels. Those exposed to 0.1 ppm had an equivocal increase in abnormal sperm after the 14-week exposure period but not after the recovery period. Based on these results 0.1 ppm level of DBCP is considered as a no effect level for reproductive parameters.