Mature cystic teratoma represents 10~20% of all ovarian neoplasms in women during the second and third decades of life. Malignant transformation rarely takes place in this tumor, and is observed in approximately 1~2% of all cases. The most common malignancy developing in mature cystic teratoma is squamous cell carcinoma. The prognosis for patients with malignant transformation of mature cystic teratoma is poor and because of the rarity of malignant degeneration, the surgical and postoperative management is not established. A case of a stage IIIb squamous cell carcinoma which developed in a mature cystic teratoma in a 47-year-old female who was disease free after tumor debulking surgery and subsequent treatment of five cycles of bleomycin (30 mg iv injection Day 1), ifosfamide (1 g/m(2) iv injection Days 1-5), and cisplatin (50 mg/m(2) iv injection Day 1) is presented and issues regarding the diagnosis and management of this rare complication are discussed.