The paper concerns the syndrome of stereotyped behaviour in rats induced by disturbance of inhibition in both caudate nuclei under influence of tetanus toxin, penicillin, and pirotoxin injected in these nuclei. Stereotyped behaviour could be inhibited by administration of GABA into the same brain area, as well as by a systemic administration of haloperidol, diazepam, aminalon, and lithium chloride. The conclusion is made that the disturbance of GABA-egric control in the caudate nucleus is a significant pathogenetic condition of the hyperactive neostriar dofaminergic apparatus, appearing due to disinhibition. Both links compose the pathogenetic basis of the syndrome of stereotyped behaviour.