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 var-ious times after stroke onset. Results : In the cat model, Lac and α-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 ,-Glx, showed no significant change. During clinical study, increases in Lac and ,-Glx, and decreases in NAA were detected three hours after stroke onset. These metabolites continued to change until 72 hours had e-lapsed. The remaining metabolites, Cho, mI, and -Glx tended to be constant. Conclusion : MRS is capable of measuring and monitoring the metabolites involved in acute cerebral infarc-tion. MRS may play an important role in the investigation of pathophysiology as well as in the early diagnosis of acute cerebral infarction.