Research on increased medical care costs associated with posttraumatic sequelae has focused on posttraumatic stress disorder (PTSD). However, the provisional diagnosis of Disorders of Extreme Stress Not Otherwise Specified (DESNOS) encompasses broader trauma-related difficulties and may be uniquely related to medical costs. We investigated whether DESNOS severity was associated with greater nonmental health medical care costs in veterans receiving mental health care. Participants were 106 men and 105 women receiving VA outpatient mental health treatment. A standardized interview assessed DESNOS severity. The dependent variables consisted of primary and specialty medical treatment costs. Sequential zero-inflated negative binomial regression was used to evaluate the variance in medical costs accounted for by DESNOS severity, controlling for PTSD severity and established predisposing, enabling, and need-based health care factors. Contrary to our hypothesis, in fully adjusted models, DESNOS severity independently added a significant amount of variance to lower specialty medical care costs, whereas PTSD did not consistently account for significant variance in medical care costs. Greater DESNOS severity appears to be associated with lower specialty medical care costs but not primary care costs. These findings may indicate that patients with DESNOS symptoms are at risk for being underreferred for specialty care. (Contains 4 tables.)