Achieving abstinence from drugs is a process that unfolds over time. Motivation waxes and wanes as a function of a host of neurobiological, psychological, and environmental factors. Success may breed complacency that increases exposure to high-risk situations. Stress and life events produce negative emotional states that rekindle memories of drug use, increase urges, and decrease willpower to resist drug use. Cues that were associated with drug use in the past may be encountered unexpectedly and awaken urges to use. Lapses are common, and present a risk of becoming full-blown relapses. Th ese various risks are of concern for anyone attempting to stop drug use, but they are particularly problematic for people with SPMI given the defi cits many of them experience in the ability to exert self-control, to conduct eff ective problem solving, and to see the continuity of events over time. In addition, the prevalence of poly-drug abuse is common in this population, and diff erent substances must be targeted sequentially for most clients. In that regard, skills and motivational factors relevant for one substance will not automatically generalize to abstinence from other substances. Consequently, treatment must be extended over time so that training in skills and coping strategies can be applied across substances, to high-risk events that occur intermittently, and in periods of decreased motivation. To do this, treatment must include sessions on relapse prevention and problem solving, in which clients identify high-risk situations that are likely to occur in the future and apply the skills that they have learned to coping with these situations without drug use. Relapse prevention and problem solving (RP/PS) is the unit of BTSAS in which these issues are addressed.