Previous investigation of the neuroendocrine responses of humans exposed to highly intense, uncontrollable stress indicate that special forces soldiers (Green Berets) differ significantly from general troop soldiers (Rangers/Marines). Although the two groups did not differ when assessed prior to stress exposure, significant differences became evident during and after stress exposure. HPA axis activation was significantly less, and NE release significantly greater in Special Forces soldiers. In addition, plasma NPY release during stress was also significantly greater in these individuals. 24 hours after stress exposure, NPY and E were depleted in general troop soldiers, but not in Special Forces troops.