A modified ISIS method, for image-selected localized proton magnetic resonance spectroscopy (1H MRS), was used to determine the ratios and T2 relaxation times of proton metabolites in normal subjects and in patients with chronic infarction and MRI white matter signal hyperintensities (WMSH). First, in patients with cerebral infarctions, increased concentrations of lactate were found in the majority of patients, and N-acetyl aspartate (NAA) was reduced to a significantly greater extent than choline (Cho) or creatine (Cre). For TE = 270 ms, the raw ratios of Cho/NAA, Cre/NAA, and Lac/NAA were significantly (P less than 0.05) increased from 0.23 +/- 0.02 (mean +/- SE), 0.20 +/- 0.01, and 0.05 +/- 0.01, respectively in the normal group to 0.39 +/- 0.08, 0.37 +/- 0.05, and 0.48 +/- 0.15 in the stroke group. Also, the T2 relaxation time of creatine was significantly (P = 0.007) increased from 136 ms in normal white matter to 171 ms in cerebral infarcts. Second, in patients with WMSH, no significant change of the proton metabolite concentrations could be detected with the exception of the choline which was significantly (P = 0.003) altered. The Cho/NAA ratio, after T2 and excitation profile correction, increased from 0.47 +/- 0.02 in the normal group to 0.64 +/- 0.05 in the WMSH group. Third, in normal white matter, the concentration of N-acetyl aspartate, choline, and lactate was estimated to 11.5, 2.0, and 0.6 mM, respectively, by assuming a total creatine concentration of 10 mM.