Some patients may be predisposed to the development of more than one gynecologic neoplasm. We evaluated 130 cases of synchronous or metachronous tumors among 5967 patients followed up by The Ohio State University Gynecologic Tumor Registry for the past 44 years from 1939 to 1983. Based on primary tumor site and invasive behavior, expected incidences for a specific second malignancy were calculated by the person-years method. A second malignancy of the lower genital tract occurred in patients with cervical, vulvar, and vaginal cancers, 1.6%, 4.3%, and 9.6%, respectively, which supports the theory of multicentric cancer of the lower genital tract. Prior radiation therapy was rarely associated with increased second gynecologic malignancies (two of 41 patients, 4.9%). Four patients had three gynecologic tumors.