From a behavioral perspective, psychoactive drugs are powerful positive and negative reinforcers and drug addiction reflects an acquired syndrome in which drug reinforcement becomes prepotent in an individual’s life. The discipline of behavioral economics integrates concepts and methods from psychology and economics to understand human behavior, including importing microeconomic methods for studying choices among reinforcers. This lecture will review recent work developing the purchase task methodology, which uses microeconomic demand curve analysis to characterize the relative reinforcing efficacy of alcohol, tobacco, and other drugs. In addition to improving the assessment of individual variation in the value of a drug as a reinforcer, this approach has significantly contributed to the measurement of acute motivation in laboratory studies, to the understanding of the neural basis of drug consumption decision making, and to understanding treatment mechanisms. As such, the purchase task approach provides a translational platform for advancing both basic and clinical science.