We assessed whether postgastrectomy polyneuropathy associated with thiamine deficiency is clinicopathologically identical to beriberi neuropathy, including a biochemical determination of thiamine status. The typical presentation for the two etiologies was as a symmetric sensorimotor polyneuropathy predominantly involving the lower limbs. In both groups, the main electrophysiologic findings were those of axonal neuropathy, most prominently in the lower limbs. Sural nerve biopsy specimens also indicated axonal degeneration in both groups. Subperineurial edema was commonly observed. Thiamine-deficiency neuropathies due to gastrectomy and dietary imbalance are identical despite variability in their clinicopathologic features and suggested that thiamine deficiency can be a major cause of postgastrectomy polyneuropathy. Characteristics of alcoholic neuropathy have been obscured by difficulty in isolating them from features of thiamine-deficiency neuropathy. We assessed 64 patients with alcoholic neuropathy including subgroups without and with coexisting thiamine deficiency. Thirty-two patients with nonalcoholic thiamine-deficiency neuropathy also were investigated for comparison. We concluded that pure-form of alcoholic neuropathy was distinct from pure-form of thiamine-deficiency neuropathy, supporting the view that alcoholic neuropathy can be caused by direct toxic effect of ethanol or its metabolites. However, features of alcoholic neuropathy is influenced by concomitant thiamine-deficiency state, having so far caused the obscure clinicopathological entity of alcoholic neuropathy.