Comprehensive exposure-based approaches to treating posttraumatic stress disorder (PTSD) are effective, but they are time intensive and not widely used because of factors such as client noncompliance and fears of iatrogenic effects. Exposure by writing disclosure (WD), modeled after Pennebaker's brief stress-reduction procedure, may circumvent these obstacles. WD treatment reduces PTSD symptoms in trauma victims but has rarely been tested in diagnosed PTSD participants and never in substance use disorder (SUD) populations--despite high comorbidity rates. The authors applied a standard Pennebaker WD treatment for 45 SUD inpatients screened for full or subsyndromal PTSD in an uncontrolled study. Results suggested potential strong cost-effectiveness: Posttreatment outcome measures showed significant symptom reductions, which remained stable at 3-month follow-up. With converging evidence from future controlled studies, WD strategies may emerge as effective and easily implemented treatment options for PTSD in SUD treatment settings. (Contains 2 tables and 2 figures.)