This paper investigates the thesis that sex role definitions in the U.S. support a double standard in societal reactions to mental incompetence. Role expectations for women are such that females are generally expected to be less competent than males in a variety of instrumental tasks, although perhaps more expressive. Males in turn are expected to be more active and aggressive than females in their exercise of the greater power and responsibility ascribed to them. In light of these generalized expectations we suggest that incompetence in instrumental fields is more disturbing when demonstrated by males, and we hypothesize that societal reactions to the mental deficiencies of males are more prompt and severe. The paper supports this hypothesis with data suggesting that mentally retarded males are more likely to be institutionalized than retarded females, and that males tend to be institutionalized at earlier ages and for milder disorders. It is noted that these data are consistent with previously reported data on mental illness (Tudor et al.).