This chapter reviews the behavior-pharmacology literature that has systematically addressed antecedent control, with particular focus on the antecedents to drug self-administration and abuse. It explores three areas of research: drugs as discriminative stimuli, classically conditioned antecedents to drug use, and operantly conditioned antecedents to drug use. When behavior pharmacologists address antecedents in the three-term contingency, they typically are interested in examining the discriminative functions of drugs. If recovering drug abusers can be trained to recognize the physiological cues of the conditioned response and use them to set the occasion for drug-avoidance responses, classically conditioned responses to drug-related cues could become an asset. Stimulus control of drug self-administration by environmental stimuli has been suggested on the basis of a variety of nonhuman studies. The likelihood of reinstating drug self-administration after a period of extinction is increased by introducing stimuli that were present when drug self-administration was established.