The technic of posterior colpotomy is described. The patient is put in the lithotomy position and conditions for possible contraindications are determined. The incision in the cul-de-sac is made well posterior in the fold between the uterosacral ligaments. The fascia is pushed downward with the index finger, displacing the rectum and exposing a widearea of thin peritoneum. The peritoneum is then opened without danger of injury to the bowel. The ovary is palpated with the index finger and grasped with a ring forceps bringing it up and medial, exposing the tube. When the uterus is anterior, gentle pressure is made over the fundus abdominally and the lateral aspect of the incision is elevated exposing the ovary. Lifting the ovary anterior and medial with pressure over the fundus abdominally facilitates exposure of the cornual portion of the tube. The incision is closed with interrupted mattress sutures including all layers. Colpotomy is a safe, certain method of confirming the diagnosis of tubal pregnancy. It is more accurate than needle aspiration of the cul-de-sac. Contraindications of this method include severe hemorrhage, shock, previous pelvic operations with extensive adhesions, endometriosis of the rectovaginal septum, fixed pelvic pathology and acute vaginitis.