A 42-year-old woman became pregnant for the second and third times following insertion of an IUD in the puerperium of her first pregnancy. The IUD was thought to have been expelled. Nineteen years after insertion, the woman developed abdominal pain and diarrhoea. A sigmoid stricture was diagnosed by endoscopy. Laparotomy showed that the IUD had perforated the uterus and penetrated the sigmoid colon. Resection was performed. This case demonstrates the need to investigate every case of a missing IUD.