Drug abuse treatment is frequently not a single occurrence in the life of a drug abuser but can be a recurring phenomenon. The proposed research reconceptualizes drug abuse treatment in terms of its episodic nature over the life cycle and will have important implications for identification of types of drug treatment clients and the provision of effective services for those types. The proposed research will address two major objectives: (1) describe the drug abuse treatment career and (2) model the drug abuse treatment career and its effects on treatment outcomes. Based on these objectives, several specific aims guide the proposed research: (1) develop measures of the drug abuse treatment career; (2) characterize drug treatment careers in terms of typologies; (3) examine the correlates of the drug treatment career; (4) model the rate of entry to treatment during the treatment career; (5) model the rate of return to treatment for a specific treatment episode; and (6) model aspects of the treatment career. Analysis techniques include modeling of the treatment career with event-history analysis techniques that describe the timing of treatment episodes during the drug treatment career.