This study was performed to determine the cause of reduced fertility after selective or complete ablation of the male accessory sex glands (ASG) in the golden hamster. The ASG (ampullary gland, coagulating gland, dorsal prostate, ventral prostate and seminal vesicle) were removed bilaterally. The following results were observed in matings involving such surgically-treated males. (1) Fertilization rate was not changed. (2) Total removal of all ASG resulted in significantly fewer sperm reaching the oviduct 1.5 h after mating and a higher rate of embryonic death at day 9 of pregnancy in the mated females. (3) Absence of the ampullary gland and ventral prostate led to higher rates of embryonic death by day 9 of pregnancy. (4) Compared with the controls, fewer oviductal sperm were found in post-ovulatory matings involving males in which the seminal vesicles had been removed. (5) No relationship could be established between the size (weight) of sperm plugs and the number of sperm found in the uterus.