A pilot project in rural El Salvador tested the integration of family planning into a water and sanitation program as a strategy for increasing male involvement in family planning decison making and use. The organizations involved posited that integrating family planning into a resource management and community development project would facilitate male involvement by diffusing information, by referring men and women to services, and by expanding method choice to include the new Standard Days Method through networks established around issues men cared about and were already involved in. This article examines data from a community-based household survey to assess the impact of the intervention and finds significant changes in contraceptive knowledge, attitudes, and behavior from baseline to endline. Because the differences between baseline and endline are greater than the differences between participants and nonparticipants at endline, the study demonstrates the power of informal networks for spreading information.