The possibility of elaboration of conditioned emotional reactions on the basis of the stimulation of the hypothalamus, was studied in cats. Reinforcement of a sound (500 c/s) by electrical stimulation of the hypothalamus, which produced reactions of undirected rage, of fear with avoidance, of food search, led to the formation of a conditioned passive defensive reaction, analogous to that based on pain reinforcement. Elaboration of conditioned emotional reactions were blocked by switching off of the sensorimotor cortex by cold. A conclusion is made that during stimulation of the hypothalamus, the state of fear serves as the reinforcing factor and that the sensorimotor neocortical areas participate in the estimation of biological significance of the conditioned signal.