The central nervous structures involved in thermoregulatory responses induced by hypothalamic or peripheral thermal stimulation were investigated in conscious rats by means of the 2-deoxy-D-[14C]glucose ([14C]-DG) autoradiographic technique. According to autoradiographs, many brain regions with significant increases or decreases in [14C]-DG incorporation were observed during thermoregulatory responses. Based on the present changes in [14C]-DG incorporation of brain regions obtained from two kinds of thermal stimulation, the following conclusions were drawn. 1) The medial preoptic area and the medial forebrain bundle are common sites for development of thermoregulatory responses being activated during cooling and warming. 2) The anterior hypothalamic area is activated during hypothalamic or peripheral warming and not during cooling. 3) The ventromedial hypothalamus, dorsomedial thalamus, caudate-putamen, globus pallidus, pars compacta of the substantia nigra, red nucleus, and the midbrain reticular formation are activated with hypothalamic or peripheral cooling. 4) The lateral preoptic area, suprachiasmatic nucleus, ventroposteromedial thalamus, pars reticulata of the substantia nigra, and the hippocampus change their activities only during peripheral cooling and warming.