<qa>  What is the main purpose of the study?Drug and alcohol abuse by people with severe and persistent mental illness SPMI is one of the most significant problems facing the public mental health system. We have been conducting a project to develop a multifaceted treatment for substance abuse in dual disordered patients Behavioral Treatment for Substance Abuse in Schizophrenia; BTSAS. Results have shown that the treatment is well-accepted by patients and has a significant effect on drug use. While BTSAS has been effective at retaining subjects and fostering reduced drug use, a major problem that occurred was low rates of engagement. The main purpose of this study is to determine if BTSAS is more effective in reducing drug use than a supportive control treatment and to determine if adding a case management component Critical Time Intervention; CTI will increase treatment engagement and retention in BTSAS. 