Voluntary sterilization is the chosen family planning method of more couples worldwide than any other, evidence of its acceptability and lack of serious shortcomings. This work offers observations on training, counseling, supervision, cost-effectiveness, and acceptability of voluntary sterilization programs, and presents some results of Profamilia's program. Training of qualified medical personnel in the available techniques is a relatively simple. Profamilia has trained almost 1000 medical professionals, nearly half of whom were from other countries, but a legal technicality has forced Profamilia to curtail training of foreign professionals. It is much more difficult to train personnel to identify and inform potential clients about sterilization, promote the procedure, and provide follow-up, yet these program activities are crucial to a successful sterilization program. Counseling of couples is necessary and should include discussion of the greater convenience of vasectomy compared to tubal ligation. Sterilization should be presented as a permanent method. This permanence, often viewed as a disadvantage, has a positive side in freeing couples of the need for further consideration of family size or contraception and in protecting them against family and social pressures to have more children. Raising marriage age or family size requirements in the hope of avoiding regret does not appear justified. Assuring that sterilization is truly voluntary is a preoccupation of donors, but has not been a problem in Profamilia programs. All clients are required to make some payment and to sign a detailed consent form. Profamilia has been persuaded to discourage mental defectives from undergoing sterilization because of possible legal problems. Periodic, unannounced visits to clinics are recommended for quality control and supervision. Profamilia employs salaried medical personnel for sterilization when careful supervision is available to ensure that they do not unjustifiably reject applicants, and pays on a per-case basis otherwise. It is estimated that each Profamilia sterilization provides 12.5 couple-years of protection. Each sterilization costs US $ 33.20 on average, 60% of it for personnel costs. Profamilia offer highly subsidized services for its lower middle class clients and almost free services for its poorest 40% of clients. The financial strain is considerable for Profamilia, which carries out some 70,000 sterilizations each year at a cost of US $ 2.25 million, only 1/7 of it directly paid for by clients. Since 1973, Profamilia has performed over 700,000 tubal ligations. There have been 19 deaths, 9 attributed to surgical and 5 to anesthetic problems. There are minor complications in about 1% of cases. 26,401 vasectomies were performed through 1990, with 2 cases requiring hospitalization.