PURPOSE: To evalvate the usefulness of single-voxel localized proton MR spectroscopy(MRS) in monitoring changes in cerebral metabolites in cases of acute cerebral infarction. MATERIALS AND METHODS: In 15 cats with common carotid artery occlusion and 21 patients with acute cerebral infarction T2-weighted (T2WI), diffusion-weighted (DWI), and MR spectroscopic images were obtained at various times after stroke onset. RESULTS: In the cat model, Lac and alpha-Glx levels increased as early as 30minutes after vascular occlusion and continued to increase for a further 2 hours. The remaini ng metabolites, NAA, Cho, mI, and alpha, alpha-Glx, showed no significant change. During clinical study, increases in Lac and alpha,alpha-Glx, and decreases in NAA were detected three hours after stroke onset. These metabolites continued to change until 72 hours had elapsed. The remaining metabolites, Cho, mI, and alpha-Glx tended to be constant. CONCLUSION: MRS is capable of measuring and monitoring the metabolites involved in acute cerebral infarction. MRS may play an important role in the investigation of pathophysiology as well as in the early diagnosis of acute cerebral infarction.