Stereotypy was produced in rats by the formation of generators of pathologically enhanced excitation (GPEE) during local disturbance of inhibitory mechanisms in the rostral part of the caudate nuclei (CN) as a result of bilateral, injection of tetanus toxin. Microinjections of gamma-aminobutyric acid (GABA) into the region of GPEE and systemic administration of haloperidol suppressed the stereotyped behavior of the animals. It is concluded that the stereotypy may be based on the formation of a GPEE as a result of disturbances in the presynaptic component of the GABA-ergic system of CN, the operant part of which consists of dopaminergic neurons.