White laboratory male rats, inbred male C57BL/6 and Balb/c mice, and male Wistar rats, all previously divided on the basis of the type of emotional reactivity, were used to compare the effects of ten peptide compounds of the tuftsin family and Selank on the behavioral manifestations of emotional stress created by a conflict situation. Peptides were shown to have positive emotional effects and antistress actions. Individual physiologically significant effects were seen, due to the molecular structures of the study peptides and/or their degradation fragments. The results demonstrate the potential for the synthesis of peptide compounds with predictable directions of pharmacological actions and safe for wide use.