The authors describe the development of combat exhaustion on the basis of their psychiatric experience with soldiers in combat. Briefly stated, they found that the majority of men adjusted adequately to combat in approximately five to seven days. They remained efficient until D+21. At about D+25 to D+30, most of them manifested abnormal fatigability, tremor, insomnia, startle reaction and generalized anxiety. This the authors designate as the 'hyper-reactive stage'. After D+40 a new group of symptoms appeared, characterized by a general slowing in mental processes and apathy which the authors call 'emotional exhaustion'. There are no attempts made to work out the psychodynamics.