To study cerebral metabolism in neonates after unilateral cerebral infarcts 4 neonates (3 full-terms, one preterm with a gestational age of 35 weeks) with unilateral cerebral infarcts were examined at 7 to 49 days of postnatal age, using proton magnetic resonance spectroscopic imaging (1H-MRSI). Three neonates had infarcts of the left middle cerebral artery (MCA), one had a right posterior cerebral artery infarct and a more localized anterior lesion. Examinations were repeated in the three fullterm infants aged 2-3 months. Lactate resonances, which are not present in normal brain after term age, were demonstrated in two patients tested at 7 and 10 days of age respectively, and in one of them lactate was still present at two months. In all four neonates a decrease of the N-acetylaspartate/choline (NAA/Cho) ratio was seen within the area of infarction. Repeated MRS of two infants at three months showed an increase in NAA/Cho ratios in all brain areas, but values remained below normal in the infarcts. In the third infant a further decrease in the NAA/Cho ratio was demonstrated in the area of infarction at two months. The NAA/Cho ratios in the surrounding and contralateral brain tissue were normal in all infants. All three infants with a MCA infarct developed a hemiplegia. The aforementioned metabolic alterations in neonates with cerebral infarcts, demonstrated using 1H-MRSI, were found to be confined to the area of infarction and abnormalities persisted beyond the neonatal period.