Anatomic examination of two bowhead whales (Balaena mysticetus) revealed an unusual combination of reproductive structures. Although the external phenotype appeared female, the gonads were found to be underdeveloped testes. In the more thoroughly studied of the two whales all derivatives of the mesonephric (Wolffian) and paramesonephric (Mullerian) ducts were absent and there was an apparently normal male karyotype (40 autosomes + XY). These findings appear consistent with a form of male pseudohermaphroditism known as testicular feminization (or androgen insensitivity syndrome) as reported in other species.