Little is known about the mechanisms underlying emotional numbing (EN). The functional relationship between other classes of posttraumatic stress disorder (PTSD) symptoms and EN is also not well understood. In the present study, we examined the statistical predictors of EN. We hypothesized that the severity of EN would be most strongly associated with the hyperarousal symptoms rather than the avoidance symptoms of PTSD, or comorbid depression or substance abuse. This prediction was derived from psychological and biological models that posit EN to be a product of the depletion of emotional resources subsequent to chronic hyperarousal. Using hierarchical multiple regression in two separate samples of Vietnam combat veterans, we found hyperarousal symptoms to be the most robust predictor of EN. These data suggest that there is a substantive relationship between hyperarousal symptoms and EN in PTSD.