OBJECTIVE. The purpose of this study was to determine the feasibility of measuring concentrations of cerebral metabolites in acute and subacute stroke patients using single-voxel localized proton MR spectroscopy and to compare these concentrations to those in contralateral brain regions and in normal healthy volunteers. SUBJECTS AND METHODS. Single-voxel proton MR spectroscopy and MR imaging were performed in 14 stroke patients, at times ranging from 2 hr to 10 days following the onset of symptoms. Signals from choline, creatine, N-acetyl-L-aspartate (NAA), and lactate were quantified in the infarcted region (n = 14) and in the hemisphere contralateral to the stroke (n = 8) and compared with data obtained from a group of 10 control subjects. RESULTS. Infarcts were characterized by significantly increased lactate (12 of 14 patients; 7.5 ± 8.9 μmol/g wet weight, mean ± SD) and significantly decreased NAA (12 of 14 patients; 5.5 ± 3.2 μmol/g wet weight), compared with contralateral brain regions and control data in healthy volunteers. Significant reductions in choline, creatine, and NAA were also found in contralateral brain regions compared with the control patients. CONCLUSION. Quantitative single-voxel proton spectroscopy is feasible for use in clinical studies of acute stroke. Ratio measurements or comparison with contralateral metabolites may be misleading because all metabolites may change during infarction, and contralateral metabolite levels may also be different from normal subjects.