Developing effective behavioral and psychological mechanisms for coping with social stress was very important in human evolution because humans evolved as social beings. The aggressive and post-aggressive behavior of 30 boys aged 7–11 years was observed during free play in summer camp with the standard “post-conflict—matched control” method (de Waal and Yoshihara, 1983). The focals were the victims of the conflict. Saliva samples for examination of cortisol and dehydroepiandrosterone sulfate levels were taken from each boy in 5 cases: 10 minutes after a conflict with and without reconciliation, matched-control samples next day and morning samples for the basal level. Every boy filled in a sociometry form, Buss-Durkee Hostility Inventory, Eysenk Personality test and the Revised Children's form for the Manifest Anxiety Scale. The stress-reduction role of peacemaking was supported on the physiological level. The level of stress-related hormones was higher when no reunion occurred.