Vietnam veterans with chronic combat-related posttraumatic stress disorder (PTSD) have been frequently reported to exhibit high levels of aggression and violent behavior. In this study, gun collection and use habits, attitudes toward violence, and self-reported levels of aggression were compared between veterans with chronic PTSD and non-PTSD veterans with equivalent histories of alcohol and substance abuse. PTSD patients reported different attitudes toward violent crime, higher levels of self-reported aggression, and a significantly higher incidence of potentially dangerous firearm-related behaviors than comparison subjects.