If consent is granted, the subject is interviewed by a member of the research team and demographic, substance use, and treatment history information is extracted from the subject's medical record. The interview consists of standardized procedures (Clinician Administered PTSD Scale [CAPS], SCID-Axis II borderline personality disorder) designed to assess PTSD and other commonly associated psychiatric disorders. A urine screen and breathalyzer are conducted to test for alcohol and other drugs. Self-report measures of depression (Beck Depression Inventory-II [BDI-II]), anxiety (Beck Anxiety Inventory [BAI]), alcohol and drug use (Addiction Severity Index [ASI] and Time-line Follow-back Calendar), treatment readiness for substance use (Stages of Change Readiness and Treatment Eagerness Scale [SOCRATES]) and for PTSD (SOC-PTSD), HIV risk (HIV-risk Screening Instrument [HSI]), and treatment utilization (Recent Treatment Survey [RTS]) are also administered. If the subject again meets criteria for PTSD (CAPS confirms diagnosis of DSM-IV PTSD), he or she is presented with the opportunity to receive the PTSD cognitive behavioral therapy. In either case, the subject receives $25 for participating in the interview.