This paper looks beyond the broad notion of social capital - which has been applied to a number of different phenomena -in order to clarify (i) the range of different elements that are encompassed by the term; and (ii) what needs to be done to further statistical research and development in order to lay the groundwork for establishing guidelines for better comparative measures in the future. The paper starts by describing the origins of the concept of social capital and the evolution of different approaches in the literature on this subject: it argues that there is not one single interpretation of social capital but rather several different approaches, which need to be more clearly distinguished in order for research and measurement to advance. The paper identifies four main ways in which the concept of "social capital" has been conceptualised and measured -- i) personal relationships; ii) social network support; iii) civic engagement; and iv) trust and cooperative norms -- reflecting different views of what social capital 'is' and implying different research agendas. The paper then looks at each of these four area in turn, assessing their meaning, functionings, and areas of policy relevance. Finally, the paper looks at measurement issues, providing examples of the measures on each of the four areas from national and international surveys. Recommendations for further statistical work in the field of social capital measurement are supported by a database of the survey questions used in around 50 surveys worldwide, available at www.oecd.org/std/social-capital-project-and-question-databank.htm.