Socioeconomic status (SES) exposures during childhood are powerful predictors of adult cardiovascular morbidity, cardiovascular mortality, all-cause mortality, and mortality due to a range of specific causes. However, we still know little about when childhood SES exposures matter most, how long they need to last, what behavioral, psychological, or physiological pathways link the childhood SES experience to adult health, and which specific adult health outcomes are vulnerable to childhood SES exposures. Here, we discuss the evidence supporting the link between childhood and adolescent SES and adult health, and explore different environmental, behavioral, and physiological pathways that might explain how early SES would influence adult health. We also address the ages when SES exposures matter most for setting adult health trajectories as well as the role of exposure duration in SES influences on later health. While early childhood exposures seem to be potent predictors of a range of health outcomes, we emphasize that later childhood and adolescent exposures are risks for other health outcomes.