Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 58 9 2020 11 19 467 469 Atefeh Moridi Preventative Gynecology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Hajar Abbasi Preventative Gynecology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Athena Behforouz Preventative Gynecology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2020 02 14 2020 05 04 One of the most common benign tumors in reproductive age women is mature Teratoma. We reported a 35-year-old woman who presented with abdominal pain, nausea, vomiting, and fever. The patient underwent laparotomy with the probable diagnosis of ovarian torsion. The evidence in the peritoneal cavity revealed chemical peritonitis due to the spontaneous rupture of the dermoid cyst. https://acta.tums.ac.ir/index.php/acta/article/view/8325