A subsample of 255 male Vietnam veterans from the National Vietnam Veterans Readjustment Study received in-depth psychiatric diagnostic interviews. This paper focuses on the 88 veterans with a war-related onset of PTSD. Among these veterans, the avoidance cluster, especially its symptoms of numbing, was most strongly associated with chronic PTSD; less strongly but also significantly associated was the hyperarousal cluster. Further analyses show that these associations are not artifacts of the relationship of symptom patterns to prewar demographic factors (race/ethnicity, socioeconomic status, age at entry into Vietnam), comorbidity, treatment and compensation seeking, or probable severity of war-related trauma. We conclude that certain symptom profiles may predict enduring pathological responses to trauma and therefore provide targets for intervention efforts.