Adenoma malignum is a highly differentiated mucinous adenocarcinoma of the cervix with a deceptively innocent histologic appearance but a highly aggressive behavior. We describe a patient who had adenoma malignum associated with Peutz-Jeghers syndrome (PJS) and bilateral ovarian sex cord tumor with annular tubules (SCTAT). The relatively frequent occurrence of cervical adenoma malignum in women with PJS warrants close surveillance by gynecologists for early detection and treatment of this cancer. We report the 16th known case of PJS with adenoma malignum and only the 8th known case of PJS with adenoma malignum and bilateral SCTAT. The highly aggressive nature of cervical adenoma malignum is exemplified, and the difficulties associated with early diagnosis are discussed. The clinical significance of cervical and ovarian tumors associated with PJS is reviewed.