Multislice proton MR spectroscopic images (SI) of the brain were quantitated, using the phantom replacement technique. In 16 normal volunteers, ranging in age from 5 to 74 years, average "whole brain" concentrations of choline (Cho), creatine (Cr), and N-acetylaspartate (NAA) were found to be 2.4 +/- 0.4, 7.9 +/- 1.3, and 11.8 +/- 1.0 (mM, mean +/- SD), respectively. These values are in good general agreement with those previously determined by single-voxel localization techniques. Cortical gray matter was found to have lower Cho and NAA levels, compared to those of white matter, corpus callosum, and basal ganglia. Cho was also found to increase significantly with age in several locations. Quantitative multislice proton Si is feasible in the clinical environment, and regional and age-dependent variations occur that must be accounted for when evaluating spectra from pathological conditions.