This article describes four alternative models for the role of client work in substance dependency treatment. The most common model is Work as a Positive Outcome, which conceptualizes work (employment) as a desirable outcome of treatment. The Work Infusion Model conceptualizes work as a therapeutic factor in treatment. The Contingent Sanctions Model requires clients to work to avoid undesirable consequences, such as losing treatment. The Work as Reinforcement Model offers paid work as a reward for treatment adherence. This article discusses whether either standard substance dependency treatment or vocational services within treatment programs increase client employment, whether clients want to work, and whether sufficient services are available. The empirical support for each model of client work is summarized. Critical issues that must be addressed in this area are outlined.