Objectives: This project is a Stage II behavioral development study designed to answer remaining critical questions necessary before disseminating Reinforcement Based Treatment (RBT) to the larger treatment community. These questions focus on the levels of intensity of RBT most efficacious for substance-using pregnant patients. Design: The proposed study utilizes a novel approach to conducting a controlled clinical trial, the sequential multiple assignment randomized trial (SMART) design. Participants (N=220) will first be randomized at treatment outset into either treatment-as-usual RBT or a reduced intensity RBT. All participants will receive a subsequent randomization based upon an assessment of their initial two weeks of treatment compliance. Early-non-compliant participants will be randomized to receive either the same or an increased level of RBT treatment intensity while early-compliant participants will be randomized to receive either the same or decreased level of treatment intensity and scope. Primary outcome measures include treatment completion, and maternal heroin, cocaine, and other illicit substance use. Secondary outcome measures include maternal measures of HIV risk behavior, and psychosocial functioning and neonatal measures of length of hospitalization, and birth outcomes. Significance: The proposed project's innovation includes: the novelty RBT, use of a cutting-edge SMART model, application of advanced statistical techniques and inclusion of a cost-effectiveness approach. The proposed project's significance is exceedingly high, as it will lay the foundation for later Stage III studies focused on dissemination of stepped care treatment programs for drug-addicted pregnant women that can be implemented not only in comprehensive care clinics but in diverse community settings that provide services to such women.