Among both civilian and veteran populations, substance use disorders (SUDs) and anxiety disorders frequently co-occur. One of the most common comorbid anxiety disorder is posttraumatic stress disorder (PTSD), a condition which may develop after exposure to traumatic events, such as military combat. In comparison with the general population, rates of both SUDs and PTSD are elevated among veterans. Recent data show that soldiers returning from Iraq and Afghanistan demonstrate high rates of co-occurring SUDs, PTSD, and traumatic brain injury. Careful assessment of these conditions is critical and may be complicated by symptom overlap. More research targeting integrated interventions for these conditions is needed to establish optimal treatments.