This paper suggests that the main reasons why populations with narrower income differences tend to have lower mortality rates are to be found in the psychosocial impact of low social status. There is now substantial evidence showing that where income differences are greater, violence tends to be more common, people are less likely to trust each other, and social relations are less cohesive. The growing impression that social cohesion is beneficial to health may be less a reflection of its direct effects than of its role as a marker for the underlying psychological pain of low social status. Low social status affects patterns of violence, disrespect, shame, poor social relations, and depression. In its implications for feelings of inferiority and insecurity, it interacts with other powerful health variables such as poor emotional attachment in early childhood and patterns of friendship and social support. Causal pathways are likely to center on the influence that the quality of social relations has on neuroendocrine pathways.