The aim of our study was to answer the following questions: (1) is thiamine deficient in chronic excessive drinkers; and (2) is peripheral neuropathy associated with thiamine deficiency or with alcohol intake itself? We performed direct assays of blood concentrations of free thiamine and thiamine phosphate in excessive drinkers with or without peripheral neuropathy and in control subjects. We found no difference in free thiamine concentrations between excessive drinkers with and without neuropathy, and no difference in free thiamine concentrations between the two groups of excessive drinkers and the control group. By contrast, a deficiency in thiamine phosphate was observed in each group of excessive drinkers compared to the control group. This was reflected in blood concentrations of total thiamine which were also lower in excessive drinkers than in controls. Finally, the thiamine phosphate: free thiamine ratio was slightly but significantly lower in the two groups of excessive drinkers than in the control group. Both groups of excessive drinkers showed typical moderate liver disease of alcoholic origin. In conclusion, the free thiamine fraction was not diminished in this group of alcoholic hospital inpatients. Thiamine deficiency would not therefore appear to play a determining role in the onset of peripheral neuropathy. In contrast, the phosphorylated fraction was slightly reduced, probably owing to the liver disease in these subjects. Contrary to studies using indirect assay techniques, our results suggest that thiamine deficiency is either slight or absent in chronic drinkers.