Six full-term infants suffering from perinatal asphyxia and with moderate or severe hypoxic-ischaemic encephalopathy were investigated by positron emission tomography (PET). Regional cerebral metabolic rates of glucose (rCMRgl) were determined using [2-18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) PET scans at a median age of 2.5 days (range 2-5 days). Localized increases in rCMRgl were visually observed in five infants. In a subgroup of three infants, absolute values of rCMRgl in different brain regions were calculated. In all cases the results of the PET studies were in good agreement with those of the neuroradiological, neurophysiological and clinical investigations. Information indicating pathophysiological events could be extracted earlier with PET than with conventional morphological imaging techniques. We conclude that [18F]FDG-PET scans performed in critically ill, asphyxiated infants very soon after birth provide valuable information for the prediction about neurological outcome.