Cross-cultural sex differences in achievement and career motivation of 432 Iranian and U.S. high school and college students were obtained by a multiple level generalizability perspective. The independent variables were culture, sex, age, family socialization, academic self-concept, home self-concept, social self-concept, perceived community support, perceived discrimination, and risk-taking behavior. The multiple level cross-cultural generalizability analysis revealed that the major portions of dependent variable variance were accounted for by interaction terms. For achievement motivation, 78% of the variance was attributable to a culture x sex x age interaction. For career motivation, the majority of the variance (between 52% and 78%) was accounted for by interaction terms of sex x culture, sex x age, age x academic self-concept, and age x home self-concept. These results suggest that motivation is a function not only of personological and situational factors but of cultural differences. (Author)