Comparison was made between the short term effects of vasoligation and open-ended vasectomy in the rat at 2, 4 and 8 weeks after surgery. Epididymal granulomata were observed in 2/5 and 1/5 rats respectively 2 and 4 weeks after vasoligation. No epididymal granulomata were observed following open-ended vasectomy, providing some support for the suggestion that this procedure may be beneficial in reducing early post operative complications in the epididymis. An unexpected observation in the 2 week open-ended vasectomy group was the finding that in 2 of 5 animals the proximal end of the vas had been temporarily obstructed by overgrowth of a fibromuscular cap. Increased distal cauda epididymidis tubule diameter in these animals suggested an increased intratubular pressure. No sustained differences were seen in the incidence of granulomata or in the response of the testis or epididymis to either vasectomy procedure by 8 weeks. The results suggest, because of the high incidence of granulomata formation following vasoligation in the rat, that by 8 weeks after surgery both vasectomy procedures are equally effective in preventing further damage in the epididymis caused by elevated intraluminal pressures.