An example of a proliferating Brenner tumor, an entity only recently delineated as an intermediate variant between benign and malignant forms is presented. Recognition of this entity, characterized by an unusual degree of papillary proliferation of Brenner-type rests, is impoitant in order to prevent confusion with either frankly benign or more aggressive malignant ovarian tumors. Reported cases, thus far, suggest a relatively favorable prognosis.