The proportion of patients with Korsakoff psychosis (KP) who have a history of Wernicke's encephalopathy is smaller in recent studies compared to previous studies. Neuropsychological tests, magnetic resonance imaging (MRI), and single photon emission computed tomography were conducted in eight patients with KP, only four of whom had had a documented Wernicke episode. All subjects showed amnesia without intellectual deterioration. MRI abnormalities were seen in each group to the same extent (atrophy of mammillary bodies, to a less extent thalamus and some generalized gyral atrophy). No MRI measure differentiated the groups. Cerebral blood flow showed reduction of flow to the anterior temporal regions bilaterally, extending to the parietal lobes, to the same degree in each group. Despite the small number of patients examined, the study supports the belief that patients with an insidious onset of KP have the same pathology as those with classical Wernicke-Korsakoff syndrome. This raises the question of whether episodes of alcohol withdrawal without adequate thiamine protection result in occasionally subclinical Wernicke's events, followed by a subsequently diagnosable KP.