This comprehensive volume analyzes dual markets for regulated substances and services, and aims to provide a framework for their effective regulation. A "dual market" refers to the existence of both a legal and an illegal market for a regulated product or service (for example, prescription drugs). These regulations exist in various countries for a mix of public health reasons and historical/political/cultural ones. Allowing the legal market to thrive, while trying to eliminate the illegal market, provides a unique challenge for governments and law enforcement.