The goal of this study was to evaluate the initial efficacy, feasibility, and acceptability of Seeking Safety (SS) treatment in a sample of incarcerated women with comorbid substance use disorder (SUD) and comorbid post-traumatic stress disorder (PTSD). Seeking Safety, a cognitive-behavioral psychotherapy treatment, is a psychosocial treatment for women with comorbid PTSD and SUD and, at the time this study was conducted, it was the treatment with the most efficacy data for this population. SS treatment appears to be a promising intervention for incarcerated women with PTSD and SUD because (1) the treatment targets many of the deficits found in this population that may interfere with their recovery and place these women at risk for reoffending (such as impulsiveness, anger dyscontrol, and maladaptive lifestyle activities), and (2) it teaches skills to manage these problematic behaviors. This study aimed to conduct an open feasibility trial of Seeking Safety treatment in a sample of six incarcerated women with SUD and PTSD and to conduct a randomized controlled pilot study to evaluate the initial efficacy, feasibility, and acceptability of the proposed treatment as an adjunct to treatment as usual (TAU), compared to a TAU control group in a sample of 22 incarcerated women with comorbid PTSD and SUD. The primary hypothesis was that, compared to the TAU condition, women in the SS treatment condition would have less severe drug and alcohol use as well as fewer PTSD symptoms and legal problems after intervention, and at six weeks and three months after release. The first six participants recruited for the study received SS group treatment as an adjunct to the treatment provided by the Discovery Program, the substance abuse treatment program in the minimum security arm of the Women's Facility of the Adult Correctional Institution in Providence, Rhode Island. The remaining participants were randomly assigned to either the control group (TAU) or to a group that received SS treatment as an adjunct to TAU. The treatment groups were conducted by clinicians who worked as substance abuse therapists in the Discovery Program and a clinical psychologist from Brown University. All SS therapists received training in delivering SS therapy from Dr. Lisa Najavits, who developed SS treatment. Assessments were conducted at pretreatment, post-treatment during incarceration, and three and six months postrelease for PTSD-related measures. Measures of severity of substance abuse and legal problems were taken at pretreatment, as well as at the six- and 12-week postrelease intervals. Measures were taken with a variety of clinical instruments, including the Addiction Severity Index (ASI), the Structured Clinical Interview for DSM-IV (SCID) module on substance use, the Clinician Administered Post-Traumatic Stress Disorder Scale-I (CAPS-I), the Trauma History Questionnaire (THQ), the Helping Alliance Questionnaire-II (HAQ-II), the Client Satisfaction Questionnaire, and the End-of-Treatment Questionnaire. Basic demographic data were also collected from administrative records. Variables include alcohol, drug, and legal composite scores at pretreatment and post-treatment, number of relapses, whether the woman returned to prison, whether the woman lied about substance abuse, use of particular substances one month prior to prison and during lifetime, PTSD indicators of frequency and intensity, total client satisfaction scores, patients' ratings of therapists and treatment, and trauma scales for crime, sexual abuse, and physical abuse. Demographic variables include age, ethnic background, education, first time in prison, the nature of the current conviction, and number of arrests with convictions.