We conducted quantification of proton MR spectroscopy (MRS) using water signal as an internal standard, in order to quantify the concentrations of metabolites in normal adult brains and in gliomas in vivo. Single-voxel spectra were acquired using a point-resolved spectroscopic (PRESS) pulse sequence as part of the Probe. P spectroscopy package on a GE Signa Horizon Hispeed LX1.5T scanner (TR/TE/Ave = 3000 msec/30 msec/64). The volume of interest (VOI) varied from 15.0 x 15.0 x 15.0 mm3 to 20.0 x 20.0 x 20.0 mm3 for the brain. The present study included 26 healthy volunteers and 12 patients with gliomas, whose diagnoses were verified by histologic examination. The calculated concentrations of N-acetyl-aspartate (NAA), creatine (Cre) and choline (Cho) in normal hemispheric white matter were 23.66 +/- 1.94 mM (mean +/- SD), 12.97 +/- 1.44 mM, and 4.38 +/- 0.60 mM, respectively. We found they were not necessarily uniform in different parts of the brain, for example, in the pons and basal ganglia. The concentrations of NAA and Cre decreased in all gliomas (p < 0.001). Cho concentration also decreased in the glioma (p < 0.005). The NAA/Cre, NAA/Cho, and Cre/Cho ratios can distinguish normal brain from gliomas, and NAA/Cho ratio can distinguish low-grade astrocytoma from the high-grade group. The results indicate that this noninvasive method offers reasonable estimation of metabolite concentrations in the brain in vivo and therefore is useful in diagnoses of gliomas.