Research interest in extra-marital sex has increased as scholars have become aware of its role in sustaining epidemics of STDs in sub-Saharan Africa and elsewhere. While most research has used the socioeconomic and demographic features of individuals as determinants of extra-marital sexual behavior, this study examined the role played by community characteristics. Using data from the 2003 Zambian Sexual Behavior Survey for a sample of 1,118 men aged 15–59 and multilevel logistic regression techniques, the study analyzed the effects of community social and demographic characteristics on involvement in extra-marital sex while controlling for the men’s individual-level characteristics. Men’s involvement in extra-marital sex was found to vary with the characteristics of communities. The chances of men’s involvement in extra-marital sex increased with community-level ethnic heterogeneity and urbanization, decreased in commercial centers, and in communities with a demographic surplus of males, health workers active in AIDS prevention, and access to the mass media. These results show that scholars trying to understand the motivations for extra-marital sex must pay attention to the characteristics of both individuals and communities.