This review on vasectomy examines operating methods, effectiveness, short- and longterm side effects, prospects for reversal, prevalence, and program issues. Although vasectomy is 1 of the safest, simplest, and most effective methods of contraception, it has been neglected in much of the world and even where it has been widespread the number of procedures has been declining. The tendency to blame low prevalence of vasectomy on male attitudes is changing to a focus on the negative attitudes of family planning providers. 4 countries, the US, UK, India, and China, account for most of the 33 million married couples of fertile age who use vasectomy worldwide. Vasectomy is also the contraceptive method of 4-15% of couples in Thailand, South Korea, Canada, the Netherlands, and New Zealand. Possible explanations for recent declines in vasectomy procedures, apart from lack of interest of family planning providers, include increasing availability of other methods, safer and simpler female sterilization, publicity about longterm side effects in monkeys, and possible rising divorce rates. Vasectomy procedures have changed little in the past decade and few medical problems have arisen. Fewer than 1 operation in 100 fails. Surgical risks are small and serious side effects are rare. Minor swelling, bruising, or pain may be experienced but they pass quickly. Infections and deaths could be virtually eliminated if sterile procedures were followed and men were carefully counseled about what symptoms require medical attention. Large scale epidemiologic studies have proven that vasectomized men do not face increased risks of heart disease. The largest study of the pathogenic effects of vasectomy involved over 10,500 vasectomy users and controls and showed that vasectomized men had no excess risk of heart attacks, cancer, or immune system diseases, and in fact vasectomized men experienced significantly fewer deaths during the study period than the controls. Many vasectomized men develop antibodies to sperm but there is no evidence to date that sperm antibodies impair immunity to disease. Despite much research, reversal procedures remain difficult, costly, uncertain, and not widely available, and vasectomy should be considered a permanent method. Factors that have been identified as crucial to the success of vasectomy programs include strong and enthusiastic leadership, focused program design with vasectomy services separate from female methods, attention to the special needs of men in counseling and other aspects, appropriate training strategies, community based orientation with local services and personnel, and special care in screening, sterile medical procedures, and sympathetic and respectful follow-up.