Plasma concentrations of magnesium were low in 32 alcoholics and 19 patients with delirium tremens. Vitamin B 1 was lowered only in delirium tremens. After discharge, 39 patients were in remission and 12 present signs of alcoholic encephalopathy. The development of encephalopathy can be predicted when delirium tremens is associated with a low plasma concentration of magnesium and vitamin B 1 and admission. One can thus conclude that encephalopathy after discharge is not caused in alcoholics by deficiencies in magnesium or vitamine B 1 or both together.