The article concerns study of the role for serotonin-modulating anticonsolidation protein (SMAP), being in linear relation with serotonin level (Mekhtiev, 2000), in regulation of aggressive behavior. The studies were carried out on aggression (induced by electroshock) and dominant (food deprivation) behavioral models, on the 5-month-old Wistar male rats. The studies were conducted in 5 series. In the 1st series of studies, undertaken on the aggression model with application of solid-phase ELISA-test, significant downregulation of SMAP (p<0.001) was revealed in the amygdala of the aggressive animals. In the 2nd series of studies, conducted on the aggression model, single intracerebral administration of SMAP brought to significant increase (p<0.001) of aggression in the animals of the experimental group, while administration of heat-inactivated SMAP to the control animals did not have any effect. In the 3rd series of studies, carried out on the dominant model, sharp downregulation of SMAP (p<0.001) in the amygdala of the dominant animals, though sharp upregulation of SMAP (p<0.001) in their platelets (corresponds to its level in the brain cortex) relatively to the intact animals were observed. In the 4th series of studies, undertaken on the dominant model, a single intracerebral administration of SMAP to the submissive animals brought to their transformation into the dominant animals (p<0.001), maintaining for 7-day timeframe, while inactive SMAP did not have any effect. In the 5th series of studies, conducted on the dominant model, a single intracerebral administration of rabbit polyclonal anti-SMAP antibodies to the dominant animals transformed them into the submissive animals for 1 day (p<0.001), while non-immune γ-globulins did not reveal any influence. On a whole, the obtained data indicate to positive regulation of aggressive behavior in the rats by SMAP and its downregulation in the amygdala of the aggressive animals in both behavioral models is, appartently, attributed to high rate of its utilization.