Localized proton spectroscopy of the brain was performed on MS patients (n = 18) and the results are compared with those of a control group (n = 17). The experiments were performed in a 1.5-T Siemens Magnetom using the stimulated echo method and selective water suppression. Acquisition parameters were TR/TE/TM = 3000/270/30 ms, NA = 256, and Acq = 13 min. Localized volumes ranged from 8 to about 80 cc. The patients (ages 25 to 66) were at various stages of the disease. Three of the eighteen patients did not show any plaques on the MR images. VOIs were chosen to contain as much plaque volume as possible in the cerebrum white matter. In the controls and in the patients with no plaques, the VOI were localized in similar white matter regions. All spectra were characterized by the presence of Cho (3.2 ppm), PCr + Cr (3.0 ppm), and NAA (2.0 ppm). The ratios NAA/Cho and NAA/(PCr + Cr) were calculated for both the MS and the control group. The results for the three MS patients with no detectable plaques did not differ significantly from the results of the control group. The former group is, however, too limited to draw any conclusion for the moment. For the MRI positive patients, the following values were found (means +/- 1 SD); NAA/Cho = 1.98 +/- 0.33 and NAA/(PCr + Cr) = 2.16 +/- 0.14. In the normals, these values were NAA/Cho = 2.54 +/- 0.39 and NAA/(PCr + Cr) = 2.76 +/- 0.25. The results quoted are TR and TE dependent.(ABSTRACT TRUNCATED AT 250 WORDS)