One outcome measure of law enforcement effectiveness is the reduction in drug consumption which occurs as a result of law enforcement interventions. A theoretical relationship between drug consumption and retail price has promoted the use of retail price as a surrogate measure for consumption. In the current article, retail price is examined as a potential outcome measure for the effectiveness of law enforcement.The predictions regarding the relationship between law enforcement intensity and price are only partially supported by research. Explanations for the disconnect between the drug law enforcement activity and retail price include: rapid adaptation by market players, enforcement swamping, assumptions of rational actors, short-run versus long-run effects, structure of the illicit market, simultaneous changes that affect price in perverse ways, the role of violence in markets, and data limitations. Researchers who use retail price as an outcome measure need to take into account the complex relationship between drug law enforcement interventions and the retail price of illicit drugs. Viable outcome measures which can be used as complements to retail price are worth investigation.