The influence of the tuftsin analogue TP-7 (heptapeptide, including Prp-Gly-Pro in its structure) on the behavior of white male rats (Wistar strain) in "unescapable" stress (an open field test consisting of 25 squares of 0.2x0.2 m each) underwent examination. The observation was held for three minutes for three days: 24 hours before, 30 minutes after and 24 hours after the tuftsin analogue (3 mg/kg in 0.2 ml distilled water) intraperitoneal administration. There was measured the motor activity: vertical and horizontal (the number of squares passed in the central area and peripheral zone, the number of passes across central area); time of freezing, grooming and orientation - searching activity (scenting the air in the corners of the open field). In comparison to control groups (1. without any treatment and 2. which received intraperitoneally 0.2 ml distilled water), tuftsin did not show a significant influence on behavior of rats, except prolongation of the time of orientation - searching activity 24 hours after its treatment (p<0.001). Tuftsin had a tendency to shorten the freezing reaction and to decrease the number of passed squares both in the general and in central area. The administration of a heavy dose of TP-7 did not change Wistar rats' behavior on the administration day in a significant way. However, it had a sedative influence at 24 hours after its administration.