Two patients with acute thiamine deficiency were examined with thalamic single-voxel proton MR spectroscopy. T2-weighted images exhibited increased signal intensity. N-acetylaspartate (NAA)/creatine (Cr) ratios were low without detectable lactate. Owing to substantially decreased choline (Cho) T2, the Cho/Cr ratio was not decreased. After thiamine therapy, the NAA/Cr ratio increased, paralleling clinical improvement and reduction in the areas of signal-intensity changes.