We identified 201 individuals who obtained IQs of 85 or below in high school and participated in the Wisconsin Longitudinal Study (a prospective longitudinal study that followed sample members from age 18 through age 53). Their life course development was contrasted with their siblings who obtained IQs above 100. Life course outcomes were assessed in five domains: Education and Occupational Attainment, Family Formation, Social Participation and Support, Physical Health, and Psychological Well-Being. Compared to their higher IQ sibling, low-IQ individuals completed less schooling, had less prestigious occupations, rated themselves less physically healthy, and reported lower levels of psychological well-being. Differences were not evident, however, in patterns of family formation, social support, job satisfaction, or objective measures of physical health.