This project addresses the following question: what explains variations in types and levels of drug violence within countries similarly afflicted by drug trafficking? I tackle this question by comparing four cities that have experienced contrasting patterns of drug violence over the past two decades: Cali and Medellin in Colombia, and Culiacan and Nuevo Laredo in Mexico. These four cities have been home to major drug trafficking organizations throughout the entire study period (1984-2009) and highlight the variation in violence that can occur over time and across the same territory. I hypothesize that the interaction between two variables, the efficiency of law enforcement and patterns of political competition, shapes the incentives and capacities of drug traffickers to employ violence. In this project I will use controlled subnational comparisons and mixed methods research tools which I will develop through fieldwork conducted over the course of a year. I aim to advance the understanding of drug violence devising an analytical framework that bridges three different areas of scholarship: literature on drug trafficking and illicit markets; literature on violence by non state actors; and literature on state-business relations. I will also contribute to the understanding of drug violence by disentangling two dimensions, frequency and visibility, which appear crucial to comprehend how citizens and governments respond to different types of violence. Finally, I will introduce an often overlooked political logic into explanations of drug violence considering how the efficiency of law enforcement and the openness of political competition shape traffickers’ incentives and capacities to employ violence.