In this paper, the emotional-aversive response induced by intracerebral injection of carbachol has been studied in cats by recording their vocalization as an index of emotional behavior. The carbachol-induced responses were quantitatively mapped in the basal forebrain and diencephalic regions using the cumulative time of the animal's vocalization as a measure of response. The areas inducing the emotional- aversive response extended along two axes: 1. longitudinally along the neuraxis, from the reticular formation through the hypothalamus to the rostro-basal forebrain; and 2. vertically along the fornix, from the mediobasal hypothalamus to the septal area. The highest magnitude of the response (vocalization time) was obtained from a strip of tissue extending from the septum and preoptic area to the dorsal perifornical area, the dorsomedial hypothalamic nucleus, the paraventricular nucleus and the periventricular stratum. The pattern of distribution of reactive and nonreactive sites showed anatomic specificity, with the highest sensitivity found within the close periventricular tissue of the third ventricle. It is suggested that carbachol mapping selectively delineates the muscarinic cholinoceptive portion of the aversive, emotional brain system.