In early stage of ischemia, proton magnetic resonance spectroscopy (MRS) is able to detect metabolic changes even though conventional MR images and CT scans are generally normal or of no specific note. It is known that N-acetyl aspartate (NAA), which is present predominantly in neurons, and some metabolites containing lactate have dynamic changes in quantity from the onset of infarction. We examined 5 patients with acute cerebral infarction using multi-voxel (section) MRS called 1H chemical shift imaging (CSI), or spectroscopic imaging (MRSI), during the first 24 hours from the onset. The spectra obtained from the voxels of each patient were classified into three groups according to the characteristics of inside, border and outside of the infarcted area by reference to the superimposed T2 weighted MR images taken at the chronic stage. The "inside" voxels, in which infarction consequently developed, showed statistically a significant high lactate level (P < 0.0001). And infarction also developed in the voxels where significant reduction of NAA (P < 0.0001) was observed in the early stage. These results imply the possibility to predict the area destined to develop infarction by the profile of 1H spectra taken in the acute stage of cerebral ischemia.