Of 127,483 histopathological reports from biopsies and surgical specimens, 1490 ovarian tumors were found, including benign and malignant neoplasms; of these there were eight cases of transitional cell tumors, meaning a frequency of 0.54%. The patient's ages ranged from 33 to 70 years with an average of 49.4. The histopathological diagnoses were benign Brenner tumor in five cases, a proliferating Brenner tumor and Brenner of low malignancy grade in two cases, and transitional cell carcinoma in one case. The predominant location was left ovary. Four were solid tumors, one was solid-cystic corresponding to the proliferating tumor of low grade malignancy and to the transitional cell carcinoma. The size of tumors varied from 1.2 to 25 cm (in diameter) with on average of 11.7. The larger tumors corresponded to the cystic and the more aggressive histological patterns, suggesting that a large predominantly cystic tumor merits extensive sampling in order to exclude malignancy.