Benign mature cystic teratoma is a very common ovarian lesion. It commonly occurs during a woman's reproductive years and most often is benign. In approximately 1% to 3% of cases, however, it can undergo a malignant transformation with a very poor prognosis. The frequency of malignant degeneration of dermoid is related to age, with the highest in-cidence in the postmenopausal years. Squamous cell carcinoma accounts for 70-88% of all malignant tumors arising in the mature cystic teratom-as followed by the much rarer adenocarcinomas and carcinoids. Preoperative diagnosis is difficult due to the rarity of this tumor and its similarity to mature cystic teratoma. We experienced 3 cases of squamous cell carcinoma arising in mature cystic teratoma and report our cases with a brief review of the literature.