This report examines the causes for the escalation of the violence in Mexico. It provides a brief overview of Mexico's counterdrug efforts, a description of the major drug trafficking organizations (DTOs), the causes and trends in the violence, the Calderón government's efforts to crackdown on the DTOs, and the objectives and implementation of the Mérida Initiative and other measures the U.S. government has taken to support Mexico in its battle with the drug traffickers.