In vivo proton magnetic resonance spectroscopy of 8 children (7-16 years) with established multiple sclerosis revealed distinct alterations in regional cerebral metabolism associated with different aspects of the disease: (1) Localized proton spectra (2 to 4-ml volumes of interest) from multiple sclerosis plaques were generally characterized by a decrease in N-acetylaspartate and creatine, and an increase in cholines and myo-inositol relative to age-matched control subjects, (2) neither chronic nor enhancing plaques (by gadolinium-diethylenetriamine pentaacetic acid) during an acute exacerbation showed elevated levels of lactate or lipids, (3) spectra from adjacent white matter that did not appear suspicious in magnetic resonance images were similar to those of normal control subjects, and (4) cortical gray matter related to neighboring multiple sclerosis lesions showed a notable reduction of N-acetylaspartate. The present results show that functional impairment in multiple sclerosis is linked to gross metabolic disturbances of neuronal cell chemistry. We suggest that focal demyelination is accompanied by increased membrane precursors of proliferative turnover and is associated with secondary neuronal shrinkage or loss, perhaps extending into related cortical gray matter.