Some reports have suggested that there is no difference in cerebral metabolic rates between wakefulness and sleep. However recently Kennedy et al. and Heiss et al. reported a decrease in cerebral glucose utilization during NREM sleep measured by the using deoxyglucose method. We used a 11C-glucose method for positron emission tomography (PET) while estimating cerebral glucose metabolism during human sleep with polysomnography (PSG). This PET and PSG study was carried out on 11 healthy male volunteers ranging in age from 18 to 26 years. In order to facilitate the onset of sleep, the subjects were deprived of sleep, under observation in the lab, for a period of approximately 20 hours prior to the PSG and PET examination. All experiments were performed in the early morning, most often between 4 and 10 AM. The subjects' sleep was monitored by PSG, i.e. electroencephalogram, electrooculogram and a submental electroencephalogram, electrooculogram and a submental electromyogram. The 11C-glucose used in the experiment was prepared by the biosynthetic method developed by Lifton and Welch, using 11C produced by a baby cyclotron. The 11C-glucose solution, containing about 20 mCi of 11C activity was administered orally to the subjects. The time course of the 11C activity in the blood following the administration was determined by drawing 1 ml of blood from the antecubital vein once every 10 minutes. These samples were assayed for 11C activity in a NaI well counter. The PET images of a horizontal cross-section of the brain at 45 mm above the orbito-meatal line, were used for the analysis of the glucose metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)