The goal of the present investigation was to evaluate whether the process of assessing posttraumatic stress disorder (PTSD) in substance abuse/dependence inpatients (N = 95) as part of a research protocol influenced the diagnostic assessment conducted by clinical staff. The prevalence of current crime-related PTSD (CR-PTSD) observed with a research interview was 40% (n = 38), whereas the rate of current CR-PTSD documented in (the same) patients' discharge summaries was 15% (n = 14). An even lower CR-PTSD prevalence rate of 8% (n = 5) was obtained from a new sample of patient discharge summaries (N = 59) collected after the cessation of the research project. On chart intake reports, clinical staff documented a history of sexual and/or physical assault in approximately one-half of these patients, but PTSD was not evaluated. PTSD appears to be under-diagnosed by clinical staff in patients with substance use disorders.