The present study was conducted to evaluate the adverse effects of dibutyltin dichloride (DBTCl) on initiation and maintenance of pregnancy after maternal exposure during early pregnancy in rats. After successful mating, female rats were given DBTCl by gastric intubation on Days 0 to 3 or on Days 4 to 7 of pregnancy at 0, 3.8, 7.6, or 15.2 mg/kg. Food-restricted pregnant rats were given an amount of feed equal to the feed intake of female rats treated with DBTCl at 15.2 mg/kg on Days 0 to 3 or on Days 4 to 7 of pregnancy. Female rats were sacrificed on Day 20 of pregnancy and pregnancy outcome was determined. After administration of DBTCl on Days 0 to 3, the rate of nonpregnant females and the incidence of preimplantation embryonic loss in the 7.6 mg/kg group were significantly higher than those in the control group, and those in the 15.2 mg/kg group were significantly higher than those in the control and pair-fed groups. In females with implantations, the numbers of implantations and live fetuses and the incidence of postimplantation embryonic loss in the groups given DBTCl on Days 0 to 3 were not significantly different from those in the control group. The incidence of postimplantation embryonic loss in the groups given DBTCl on Days 4 to 7 at 7.6 and 15.2 mg/kg was significantly higher than that in the control and pair-fed groups. It can be concluded that DBTCl adversely affects initiation and maintenance of pregnancy when administered during early pregnancy and that the manifestations of the adverse effects of DBTCl vary with the gestational stage at the time of maternal exposure.