H-1 NMR spectroscopy of cerebrospinal fluid (CSF) is currently being used to study metabolic profiles characteristic of distinct multiple sclerosis (MS) manifestations. For select MS patient groups, we have previously detected significantly increased concentrations of several identified metabolites and one unidentified compound. We now present, for the first time, the identification of the latter molecule, beta-hydroxyisobutyrate (BHIB). A combination of dedicated 1D and 2D H-1 NMR experiments was employed for signal assignment. To our knowledge, BHIB has not previously been identified in H-1 NMR spectra of biofluids or biological tissues. Our assignment suggests new biochemical pathways involved in specific MS pathologies. (c) 2006 Elsevier Inc. All rights reserved.