Abstract:A 47‐year‐old man with chronic alcoholism was admitted to a psychiatric institution because of his mental symptoms and abnormal behavior. He had dementia, emotional disturbances, muscle cramps (tetanic fits), and impairment of abstract thinking and psychomotor function. The biochemical examination of his blood revealed Hypomagnesemia, hypocalcemia and a low level of serum parathyroid hormone. The administration of Ca lactate improved hypocalcemia and muscle cramps, but not the other symptoms. An addition of Mg sulfate did not change the clinical condition and the serum electrolyte level. From these findings a relation of chronic alcohol intake to the imbalance of serum electrolytes as well as a low level of serum parathyroid hormone was discussed, and a pathogenetic mechanism of dementia observed in this case was specula