Assessment of masculinity as an ideological belief system (MI) has become increasingly popular. Validation of MI measures and subsequent research has relied heavily on undergraduate samples. In the present study, convergent and divergent validity of the Conformity to Masculine Norms Inventory (Mahalik et al., Psychology of Men and Masculinity, 4: 3–25, 2003) were examined among a convenience sample of 688 male and female adults who were divided into four groups (undergraduates, younger adults, middle-aged adults, older adults). Across groups, convergent validity was suggested by consistent relations with sexism, and divergent validity was suggested by consistent nonsignificant relations with masculine attributes. Results suggest that generalizations among male groups can be made with caution and that generalizations to women may be appropriate when the focal constructs are unrelated to women or femininity.