In our article, we present the recent findings of our ethnographic field study on drug use and the emergence of a drug use culture in transnational communities in Mexico. Transnational communities are part of a larger migratory labor circuit that transcends political borders and are not restricted to a single locality. Transnational migrants and returning immigrants link the multiple localities through their social networks. In southern Guanajuato, Mexico, using a transnational migration paradigm, we examined the manner in which transnational migration and drug trafficking organizations are contributing to a growing drug problem in these communities. We found that transnational migrants and returning immigrants, including deported workers, introduce drugs and drug use practices, and contribute to the creation of a drug use culture within the communities. The social conditions in the community that foster and proliferate drug use are many: the erosion of the traditional family, truncated kinship bases, and new social formations. These conditions are all consequences of migration and emigration. Recent drug cartel activities are also contributing to this growing drug problem. The cartels have aggressively targeted these communities because of availability of money, existing drug use, a drug use culture, and the breakdown of traditional deterrents to substance abuse. Although a number of communities in three municipalities were part of our study, we focus on two: Lindavista, a rancho, Progreso, a municipal seat. Our field study in Mexico, one of four sequential ethnographic field studies conducted in Guanajuato and Pennsylvania, was completed over a six month period, from September, 2008, through February, 2009, using traditional ethnography. The four field studies are part of a larger, ongoing, three-year bi-national study on drug use among transnational migrants working in southeastern Pennsylvania. This larger study, near its third and final year, is funded by the National Institute of Drug Abuse.