Vasoresection has great significance as a method of contraception. Next to surgicial sterilization of the female it is the most reliable method of contraception if surgical technical errors are avoided and postoperative speriograms are carried out. According to a review by Leader (2711 cases), 1 patient in 400 remaining capable of procreation must nevertheless be reckoned with. The failure is due to the fact that the surgeon did not identify a vas deferens or a spermatogranuloma led to a spontaneous recanilization. For this reason ths stumps of the vas should be stitched round. The question of electrocoagulation of the intima with ligature of the adventitia also arises.