Longitudinal change of the proton spectroscopy was observed in 2 cases of cerebral infarction. Proton spectra was acquired utilizing stimulated echo acquisition mode (STEAM). In acute stage, the increase of lactic acid and decrease of N-acetyl-aspartic acid (NAA) was observed prior to the appearance of abnormality in imagings such as magnetic resonance imaging and computer tomography. The increase of lactic acid was observed in subacute stage and chronic stage (in severe case). The decrease of NAA persisted in chronic stage. The increase of lactic acid and decrease of NAA indicate a damage of the ischemic tissue. The degree of the decrease of the NAA seems to be a reasonable indicator of the viability of the damaged tissue. The proton spectroscopy is a powerful modality for the evaluation of the extent of tissue damage caused by the ischemic insult.