This article uses the concept of social networks as it is employed in the research literature on family planning and migration to explore the impact of out-migration on modern contraceptive knowledge and use in rural Guatemala. Data for this study come from the 1995 Guatemalan Survey of Family Health. Results from multilevel regression models indicate that urban migration experience, having migrant kin in urban or international destinations, and living in a community where urban migration is common are all associated with greater contraceptive knowledge. Social ties to urban or international migrants are also associated with a greater likelihood of modern contraceptive use among married women, but this association works primarily through increased contraceptive knowledge. The findings of significant diffusion effects provide support for recent theories of fertility decline that emphasize the role of social interactions.