Most non-neoplastic lesions of the ovaries have not been comprehensively examined in the contemporary literature. We evaluated completely embedded ovaries from 403 unselected, consecutive patients who had grossly normal adnexa. These included prophylactic specimens in high-risk women with BRCA mutations (38 women) and women with a personal history of breast cancer or a family history of breast and/or ovarian cancer (79 women). Transitional cell (Brenner) nests were found in 9.1%; 31% of these lesions were smaller than 1 mm, and 8 were solitary nests. Cortical granulomas were found in 20.5%, fatty metaplasia in 5.3%, mucinous metaplasia of surface epithelial inclusions in 5.5%, and smooth muscle stromal metaplasia in 2%. One or more types of stromal hyperplasia were found in 24.3%. Endometriosis was found in 22% of adnexa. There were no significant differences in the findings in high-risk women compared with non-high-risk except those attributable to age differences between the groups. These findings establish baseline frequencies for non-neoplastic ovarian lesions, and suggest that transitional cell nests are so common that they can be regarded as a normal finding.