The case reported in this paper demonstrates the difficulties in establishing the diagnosis of type 2 uterine perforation incident to the use of an IUD. A type 2 perforation is considered to have occurred when the IUD is entirely within the myometrium, no part of the IUD can be detected in the uterine cavity, and no part can be visually detected in the peritoneal cavity. The patient, a 28-year old gravida 3, para 2, had an IUD inserted 18 months prior to admittance, 7 weeks after her 2nd delivery. 1 year later she became pregnant. During a therapeutic abortion, the IUD string was removed without the device, which was considered to be outside and behind the uterus. Ultrasonography revealed that the IUD was inside the posterior uterine wall, parallel to the endometrial mucosal lining, with no connection to the uterine cavity. Other diagnostic methods used in this case included plain abdominal films, hysterography, and hysteroscopy; however, neither these methods nor uterine palpation suggested that there was an IUD in the uterus. The original diagnosis was later confirmed by intraoperative radiography, and the IUD was removed through a small incision on the posterior uterine wall. This case demonstrates the useful role of ultrasonography in the work-up of a woman with a missing IUD. It is suggested that ultrasonography be used following difficult IUD insertions or postpartum insertions, since most perforations occur in such cases. Partial and complete uterine perforation is considered more likely when the IUD is inserted during the 1st 3 months postpartum.