The aim of this article is to provide an overview of the concept of social capital and to distinguish its different forms, focusing on their potential effects on health. According to many scholars, social capital comprises social networks, norms of reciprocity or social support and social trust. In this article the core element, the social network, has been further distinguished by the direction of ties and levels of formality, strength and diversity. In the past few years there has been increased interest in social capital in the health field and a great deal of research has suggested that social capital is generally positively related to health. However, little research has been conducted into how different forms of social capital or social networks influence health. What is the difference, for instance, between bonding and bridging social capital in terms of health outcomes? It is important to distinguish the different forms because they imply different resources, support and obligations. More research needs to be conducted into the different forms of social capital and their effects on health. A special focus should be placed on the health impacts of cross-cutting - or bridging and linking - forms of social capital.