Clinical T2 and contrast-enhanced T1-weighted MRI have become the diagnostic modalities of choice to evaluate multiple sclerosis (MS) due to their sensitivity to acute, often subclinical events in the brain and their ability to measure the accumulation of lesions over time. MRI, however, lacks specificity, in that to date, there are conflicting reports concerning the number and volume of these lesions, &#147;load of the disease,&#148;and the neurological deficits. Furthermore, clinical MRI is blind to occult white matter (WM) and especially most gray matter (GM) pathology. The need for more reliable surrogate markers frequently leads to proton magnetic resonance spectroscopy (1H-MRS) being used to probe the underlying metabolism of normal appearing WM (NAWM) and its lesions. Since MS pathogenesis starts on molecular cellular levels, we propose to use state of the art, short echo-time, three-dimensional high-spatial resolution local and global 1H-MRS methods to examine three hypotheses: H1: That MS lesions develop in WM regions which are already metabolically abnormal;H2: Abnormal metabolic activity persists in NAWM and lesions even absent Gd-enhancement (the current marker of &#147;activity&#148;);and H3: That global whole-brain quantification of the decline rate of the neuronal cell marker N-acetylaspartate (NAA) reflects the aggressiveness of a patient&#146;s disease, and therefore, could forecast its future course in that individual. These hypotheses will be tested by continuing to follow a cohort of 25 relapsing-remitting (RR) MS patients and 25 matched controls, for 5 more years, with three Specific Aims: Specific Aim 1 is to perform longitudinal follow-up of the overall metabolites levels in the NAWM to establish markers for current MRI-occult disease activity. Specific Aim 2 is to follow localized metabolism in NAWM to determine what focal changes preceded lesion formation and determine those lesions outcome - to repair or become chronic. Specific Aim 3 is to correlate the NAA levels of the whole brain and its WM and GM fractions with the patients'clinical deficits to establish the NAA as a forecaster of disease severity. The health relatedness of this study is its prospect to establish, quantify and validate non-invasive metabolic surrogate markers of RR MS progression that will enable us to: (i) Gauge current level of disease activity, thereby, (ii) increase our capability to forecast its future course for these (young) patients;and consequently (iii) lead to improved monitoring of response in drug and treatment trials.