This treatment intervention trial is designed for men and women with substance dependence and comorbid Post-Traumatic Stress Disorder (PTSD). Participants will be randomly assigned to one of three conditions (two behavioral treatments [Concurrent Treatment of PTSD and Substance Use Disorders Using Prolonged Exposure and Relapse Prevention Therapy] and an active monitoring control group) and will be evaluated at baseline and four follow-up points (post-treatment, 1-month, 2- month and 3-month post-treatment).

This study will enhance the knowledge and understanding of concurrently treating individuals with substance use disorders and PTSD in hopes of facilitating treatment retention and increasing the likelihood for more positive treatment outcomes. Following NIDA's stage model for behavior therapies development, this study will take the next step building upon promising findings from Stage IA work with an exposure-based therapy modified to use safely with substance dependent individuals.

This study is a randomized clinical trial to assess the relative efficacy of two active treatment conditions versus an active monitoring control group for substance dependent individuals who also meet criteria for current PTSD according to the diagnostic standards set by the DSM-IV. Eligible participants will be randomly assigned to either: (1) Concurrent Treatment of PTSD and Substance Use Disorders Using Prolonged Exposure (COPE); (2) Relapse Prevention Treatment (RPT) or an (3) Active Monitoring Control Group (AMCG). The study is a three armed randomized controlled trial with repeated outcome measures at post treatment and 1-,2-, and 3-months post-treatment follow-up points for participants in COPE and RPT.

Inclusion Criteria:

1. Men and women who are a minimum of 18 years and maximum of 65 years.
2. Participants meet DSM-IV criteria for current or past substance dependence
3. Participants must have used alcohol or other drugs within the past 3 months
4. Participants must speak English
5. Participants must meet DSM-IV criteria for current PTSD in response to on an interpersonal, civilian trauma
6. Participants are capable of giving informed consent and capable of complying with study procedures.
7. Participants demonstrate no gross organic mental syndrome

Exclusion Criteria:

1. Participants who are currently suicidal or homicidal
2. Participants who carry a diagnosis of BiPolar I or psychotic disorders are exclusionary.
3. Participants receiving PTSD-specific treatment
4. Participants on anxiolytic, antidepressant or mood stabilizing medications which have been initiated during the 8 weeks prior to study participation
5. Participants refusing to be audio or video taped