Interest in social capital and health has emerged at an exciting time. In public health, there is a renewed interest in mechanisms that link social inequalities and health. In epidemiology, there has been a critical interrogation of methods and a call for a more explicit use of theory. In health promotion over the last 20-30 years, social health interventions have been somewhat marginalised in an era dominated by interest in traditional cardiovascular disease risk factors. Now that social hypotheses are being reborn in health, there is a risk that the sophistication that has developed in social health promotion and the literatures that have informed it could be overlooked. In this paper, we present a brief history of social capital and how it has come into recent prominence through the debate linking income inequality and health. We present the background to this, the earlier literatures on social environmental influences on health and the possible processes thought to underlie this relationship. Social capital has relational, material and political aspects. We suggest that, although the relational properties of social capital are important (eg, trust, networks), the political aspects of social capital are perhaps under recognised. The paper also reviews how complex social processes at the community level have come to be operationalised by social theorists and intervention agents in other fields. We suggest that social capital research so far has inadequately captured the underlying constructs, in particular the qualitative difference between the macro/context level and the micro/individual level. While being cautious about the science, we conclude that social capital's power as rhetoric and as a metaphor may be of value. We conclude by suggesting that the coalescence of interests in context-level influences on health now invites a revitalisation of theories and interventions inspired by diverse fields, such as geography and ecological community psychology.