A complete understanding of the consequences of service in a war zone includes examining the lifetime and current prevalence of post-traumatic stress disorder (PTSD), and of partial PTSD. Cases of partial PTSD are persons who have clinically significant symptoms of PTSD, but who do not meet the full diagnostic criteria. The National Vietnam Veterans Readjustment Study (NVVRS) estimated the lifetime prevalence of PTSD to be 30.9% among male theater veterans, 26.% among females; lifetime prevalence of partial PTSD was an additional 22.5% and 21.2%, respectively; current prevalence of partial PTSD was 11.1% in males and 7.8% in females. NVVRS findings indicate that of the 1.7 million veterans who ever experienced significant symptoms of PTSD after the Vietnam war, approximately 830,000 (49%) still experience clinically significant distress and disability from symptoms of PTSD. The contribution of partial PTSD represents an estimated additional 350,000 veterans. © 1992 Plenum Publishing Corporation.