Proton magnetic resonance spectroscopic imaging (MRSI) of brain was performed on 53 patients with clinically definite relapsing remitting multiple sclerosis (MS). The contributions of white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) to the spectroscopic voxels were determined using either double inversion recovery magnetic resonance imaging or segmentation of affirmative images. In 13 patients additional peaks in the 0.8 to 1.5 ppm spectral region, that reflect the demyelinating products were observed mainly confined to GM. These studies demonstrate that some of the GM that appears normal on magnetic resonance images is biochemically abnormal.