In response to the widespread consensus on the importance of social capital, and to concerns about the scarcity of institutions giving voice to disadvantaged groups, some donors have begun programs designed to strengthen indigenous community organizations. We use a prospective, randomized evaluation to examine a development program explicitly targeted at building social capital among rural women's groups in western Kenya. The program increased turnover among group members. It increased entry into group membership and leadership by younger, more educated women, by women employed in the formal sector, and by men. The analysis suggests that providing development assistance to indigenous community organizations of the disadvantaged may change the very characteristics of these organizations that made them attractive to outside funders.