This study investigated the hypothesis that socioeconomic differences in health status change can largely be explained by the higher prevalence of individual health-risk behaviors among those of lower socioeconomic position. Data were from the Americans' Changing Lives study, a longitudinal survey of 3,617 adults representative of the US non-institutionalized population in 1986. The authors examined associations between income and education in 1986, and physical functioning and self-rated health in 1994, adjusted for baseline health status, using a multinomial logistic regression framework that considered mortality and survey nonresponse as competing risks. Covariates included age, sex, race, cigarette smoking, alcohol consumption, physical activity, and Body Mass Index. Both income and education were strong predictors of poor health outcomes. The four health-risk behaviors under study statistically explained only a modest portion of the socioeconomic differences in health at follow-up. For example, after adjustment for baseline health status, those in the lowest income group at baseline had odds of moderate/severe functional impairment in 1994 of 2.11 (95% C.I.: 1.40, 3.20) in an unadjusted model and 1.89 (95% C.I.: 1.23, 2.89) in a model adjusted for health-risk behaviors. The results suggest that the higher prevalence of major health-risk behaviors among those in lower socioeconomic strata is not the dominant mediating mechanism that can explain socioeconomic disparities in health status among US adults.