Spontaneous rupture of mature cystic teratoma occurs rarely, but may lead to a chemical peritonitis. Once rupture of mature cystic teratoma is diagnosed, immediate surgical intervention is necessary. Removal of ruptured ovarian cystic teratoma and copious lavage of abdominal cavity are usually suffi cient to prevent prolonged chemical peritonitis. We report here a rare case of spontaneously ruptured ovarian cystic teratoma diagnosed by computed tomography scan obtained before and after the rupture, and in which chemical peritonitis lasted over 2 months after surgery.