A vasectomy is one of the most popular and effective male contraceptive methods available today. An estimated half-million American men have vasectomies performed each year. The procedure typically takes about a half-hour and usually causes few complications. Best of all, there is no change in sexual function.

Many couples choose this means of birth control because a vasectomy is less invasive than a tubal ligation, the procedure used to prevent a woman's eggs from reaching the uterus, and because it also is more easily reversed.

In a vasectomy, a surgeon performs a simple procedure to cut and close off the vas deferens, the tubes that carry sperm from the testes. As the sperm- and testosterone-producing organs, the testes are located in a sac at the base of the penis called the scrotum. Each testicle is connected to a small, coiled tube called the epididymis, where sperm are stored for as long as six weeks while they mature. The epididymes are connected to the prostate gland by a pair of tubes called the vas deferens.

The patient typically remains clothed from the waist up and lies on his back. The scrotum is numbed with one or more injections of local anesthetic (lidocaine), the vas deferens is gathered under the skin of the scrotum, and a small incision (usually 1 centimeter or less) is made. The vas deferens is then pulled through the incision, cut in two places, and a 1-centimeter segment is removed.

Each end of the vas deferens is surgically tied off or clipped, and placed back in the scrotum. The incision is sutured and the procedure is repeated on the other side of the scrotum. Some urologists cauterize the ends of the vas deferens, but others find that cauterization complicates reversal and is unnecessary.

The incisions are dressed and most men go home immediately after the procedure.