History of early childhood trauma was prevalent and highly correlated with Disorders of Extreme Stress Not Otherwise Specified (DESNOS) in a sample of veterans in inpatient treatment for chronic posttraumatic stress disorder (PTSD). DESNOS predicted reliable change on a variety of measures of psychiatric symptomatology (including PTSD) and psychosocial functioning independently of the effects of PTSD diagnosis and early childhood trauma history. DESNOS also predicted treatment outcome on PTSD and quality of life measures after controlling for the effects of ethnicity, war zone trauma exposure severity, initial level of symptomatic severity or quality of life, Axis I (PTSD and major depression) and Axis II (personality disorder) diagnostic status, and early childhood trauma history. Early childhood trauma was not predictive of outcome. DESNOS appears to play an important role in assessment and treatment planning for psychotherapeutic rehabilitation of chronic PTSD.