Databases from the New England Veterans Integrated Service Network were analyzed to determine factors associated with long-term, high-dose anxiolytic benzodiazepine prescriptions dispensed to patients with posttraumatic stress disorder (PTSD) and existing alcoholism and/or drug abuse diagnoses. Among 2,183 PTSD patients, 234 received the highest 10% average daily doses for alprazolam, clonazepam, diazepam, or lorazepam, doses above those typically recommended. Highest doses were more commonly prescribed to patients with existing drug abuse diagnoses. Among patients with PTSD and alcoholism, younger age, drug abuse, and concurrent prescriptions for another benzodiazepine and oxycodone/acetaminophen independently predicted high doses. Results indicate that for veteran patients with PTSD, alcoholism alone is not associated with high-dose benzodiazepines, but existing drug abuse diagnoses do increase that risk.