Socioeconomic status (SES) is an important predictor of a range of health and illness outcomes. Research seeking to identify the extent to which this often-reported effect is due to protective benefits of higher SES or to toxic elements of lower social status has not yielded consistent or conclusive findings. A relatively novel hypothesis is that these effects are due to chronic stress that is associated with SES; lower SES is reliably associated with a number of important social and environmental conditions that contribute to chronic stress burden, including crowding, crime, noise pollution, discrimination, and other hazards or stressors. In other words, chronic stress may capture much of the variance in health and social outcomes associated with harmful aspects of lower social status. Low SES is generally associated with distress, prevalence of mental health problems, and with health-impairing behaviors that are also related to stress. Research targeting this hypothesis is needed to determine the extent to which stress is a pathway linking SES and health.