The human demyelinative disorder central pontine myelinolysis may be an iatrogenic disease caused by a rapid rise in serum sodium, usually when hyponatremia is corrected. Rats treated with hypertonic saline after 3 days of vasopressin-induced hyponatremia had demyelinative lesions in the corpus striatum, lateral hemispheric white matter, cerebral cortex, hippocampal fimbria, anterior commissure, thalamus, brainstem tegmentum, and cerebellum. Thus, rapid correction of hyponatremia can lead to demyelinative lesions and may be the cause of central pontine myelinolysis in man.