PIP: A case of uterine perforation by an IUD with acute and chronic irritation of the appendix is presented. The patient, a 30-year old gravida 4, para 4, was admitted to the hospital with severe abdominal pain, fever, and diarrhea. A Lippes loop IUD had been inserted 3 years previously. The device could not be visualized at laparoscopy. At laparotomy the IUD was palpable within a large inflammatory mass in the right lower abdomen . Dissection of the adhesions revealed the IUD twisted around the appendix, and appendectomy was performed. This is the 1st reported case of a perforated, nonmedicated IUD causing appendicitis. The 2 cases of IUD appendicitis previously described in the literature involved Copper-7 devices, which have been shown to cause considerable tissue response when placed in the peritoneal cavity. Abdominal signs and symptoms associated with a missing IUD string should alert physicians to the possibility of IUD appendicitis.