The EEG spectral analysis applied to electrical brain activity of rabbits in the state of animal hypnosis revealed a 2-4-fold increase in the power of the sigma frequency band (12-17 Hz) and a 1.5-2-fold decrease in the gamma frequency (especially 40-70 Hz) in addition to well-known growth of delta (0.3-3 Hz) and reduction of theta activity (4-8 Hz). The changes were more prominent in the frontal cortex areas. The influence of hypnotic state on cortical gamma activity pharmacologically augmented by ketamine injection was analyzed. Administration of subanesthetic ketamine doses led to behavioral locomotor excitation of an animal accompanied by a long-lasting (up to 2 h) increase in the gamma electrical activity. If the animal hypnosis was induced after the ketamine injection, it resulted in an almost instant reorganization of the spectral power. The slow-wave power increased and the gamma-power decreased to the baseline levels. Thus, the animal hypnosis eliminated the reorganization of cortical rhythmicity produced by ketamine, which suggests a stabilizing and, to a certain extent, protective function of this kind of hypnosis in the states of behavioral locomotion and stress.