We focus on physical and psychosocial job characteristics as mediators in the relationship between socioeconomic status (SES) and health. From sociological research on the stratification of employment outcomes we expect that people with less education, lower earnings, and lower levels of occupational standing have more physically and psychosocially demanding jobs. From the occupational stress, ergonomics, and job design literatures, we expect that people with more physically and psychosocially demanding jobs have less favorable health outcomes. Consequently, we expect to find that job characteristics play an important mediating role in associations between SES and self-assessed overall health and cardiovascular and musculoskeletal health problems. To address these hypotheses, we use data from the Wisconsin Longitudinal Study (WLS). We find support for our hypotheses, although the extent to which job characteristics mediate SES-health relationships varies across health outcomes and by sex.