In a 5-year autopsy material constituting 6,964 autopsies, there were 52 cases of Wernicke's encephalopathy of which 12 (23%) occurred in non-alcoholics. Among 18 cases with active (acute) disease, 7 cases (39%) were found in non-alcoholics. Only 4 cases of active Wernicke's disease were diagnosed clinically, all of them in alcoholics. The predominant clinical symptoms were disorientation and depressed levels of consciousness, whereas eye symptoms were recorded in only 3 cases. None of the non-alcoholics were given specific thiamine therapy, whereas some alcoholics received large doses of the vitamin as a routine procedure. However, the thiamine therapy was often instituted too late. It is concluded that active Wernicke's encephalopathy should be considered in all patients with prolonged malnutrition and that disorientation and depressed levels of consciousness may be the predominating symptoms of the disease. Even the slightest suspicion of Wernicke's encephalopathy should prompt immediate administration of large doses of thiamine parenterally.