This paper applies behavioral economic concepts to address two behaviors frequently exhibited by the drug dependent: (a) spending a considerable amount of time, effort, and money to obtain and use drugs (often to the exclusion of other potential reinforcers), and (b) "loss of control" or the inability to follow through on plans to cut down or stop drug use. The first of these behaviors is examined in the context of two economic principles: (a) drug use covaries with drug availability and (b) drug use is affected by the availability of alternative nondrug activities or events. A review of drug abuse research (including basic, epidemiology, life history, and treatment research) demonstrates the relevance of these two principles to the phenomenon of drug dependence. The second of these behaviors ("loss of control") is conceptualized as resulting from the discounting of delayed rewards. Research demonstrating the discounting of delayed rewards in drug-abusing populations is reviewed. Behavioral-economic principles suggest drug-abuse treatment efforts should (a) use methods that decrease drug availability, (b) increase the availability of nondrug activities or events that may substitute for drug use, and (c) use treatment methods that will increase the extent to which delayed events control behavior in substance abusers.