Data from the National Vietnam Veteran Readjustment Study (NVVRS) revealed a prevalence of current posttraumatic stress disorder (PTSD) in female Vietnam Theater veterans half the size of the prevalence in their male counterparts. This stands in contrast to the elevated prevalence of PTSD in women obtained in general population surveys. This study undertakes further analyses of gender differences in the NVVRS and how these differences might be specified by the amount and type of exposure to war-zone stress. The findings indicate that male elevations in PTSD are limited to men who served under circumstances of high probable severity of war-zone stress exposure. When prewar demographic differences are controlled, male veterans in low-exposure circumstances display a level of PTSD prevalence substantially lower than female veterans.