As social inequalities in health continue to be a key public health problem, scientific advances in explaining these inequalities are needed. It is unlikely that there will be a single explanation of social inequalities in health. This introductory paper sets out one explanatory framework, exposure to adverse psychosocial environments during midlife, and particularly at work. We argue that exposure to an adverse psychosocial environment, in terms of job tasks, defined by high demands and low control and/or by effort-reward imbalance, elicits sustained stress reactions with negative long-term consequences for health. These exposures may be implicated in the association of socioeconomic status with health in two ways. First, these exposures are likely to be experienced more frequently among lower socioeconomic groups. Second, the size of the effects on health produced by adverse working conditions may be higher in lower status groups, due to their increased vulnerability. In this special issue, these arguments are illustrated by a collection of original contributions from collaborative research across Europe. The papers, in our view, advance the case for the robust associations between measures of adverse psychosocial environment and ill health, as they are based on comparative studies across several European countries and as they combine different types of study designs. This collaboration was enabled and supported by a European Science Foundation scientific programme on 'Social Variations in Health Expectancy in Europe'.