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Self-stimulation was studied in dogs chronically implanted with electrodes in different points within the basal forebrain. The animals exhibiting pure self-rewarding behavior were defined as "optimal" and "good self-stimulators", whereas those with concomitant aversive phenomena were incorporated into the third category called "self-stimulation-withdrawal". In "optimal self-stimulators" a remarkable resistance of the response to extinction was noted. A strong negative attitude toward food was found in four dogs upon stimulation of the self-rewarding loci. Penile erection accompanied self-stimulation in two animals. Sniffing at first always followed incentive brain stimulation, but later it appeared at the beginning of each experiment and/or preceded the bouts of pressing. A rise of hypothalamic temperature was noted in mast of the animals. In some cases this was equal to or exceeded 1 degree Celsius. The temperature increase was accompanied by intense panting between the bouts. Seizures appeared locally as contractions of masticatory muscles and sometimes developed into a generalized fit. Anatomically the "reward area" in the dog extends from the septum and the preoptic area to the mammillary bodies and reaches laterally to the internal capsule.