The idea of social capital is currently being discussed as a source of support for health, though it is often argued that the concept should not be used in an attempt to evolve neutral policy strategies but underlines the need for moral and political debate in health policy. This article, first, supports this argument by indicating the complex and culturally diverse nature of social capital. Its components react with their social contexts to produce a range of variants which differ from each other along several dimensions. Social solidarity and support involve different conventions in different places, with results which need appraisal before they can be supported. The article explores these issues by drawing on ethnographic material illustrating aspects of social relatedness in a variety of settings. Secondly, writers who treat social capital as invariably positive tend to associate it with conditions in the neo-liberal societies of late capitalism, even though they also see it as threatened there. Again examining social contexts, the article locates the reasons for this paradox in the cultures and structures of the societies concerned. Large-scale institutions in the West-including both those required to implement public health measures and those in which the majority of people work-are organised via neo-liberal processes which are not all conducive to the types of social relatedness which the social capital debate seeks to explore. In particular, significant aspects of social trust are difficult to support in neo-liberal organisations. The assumption that social capital can be promoted via social engineering which relies upon these very institutions is thus questionable. This, together with more positive aspects of the debate, draws attention to the need for further research on social relatedness if it is to be supported by public policy.