Four definitions of subthreshold posttraumatic stress disorder (PTSD) were compared in 815 veterans seen in Veterans Affairs Medical Center primary care clinics. We compared PTSD Checklist (PCL) scores and Short Form 36 (SF-36) scores between participants meeting criteria for one of the subthreshold PTSD definitions (based on Schnurr, Marshall, Blanchard, or Stein) to those with and without PTSD. Using regression, those meeting subthreshold criteria by any of the four definitions had lower mental and physical health functioning and higher PCL scores relative to those without PTSD; they also had higher mental health functioning and lower PCL scores relative to those with PTSD. With SF-36 physical functioning scores, only those meeting the Stein definition differed from the group with PTSD. Thus, these definitions appear to distinguish individuals who are qualitatively different from individuals with no PTSD or with PTSD and are nearly equivalent in their ability to discriminate individuals.