The hypothalamo-hypophyseal neurosecretory system (HHNS) was studied in patients dying at various intervals after the onset of the first clinical manifestations of myocardial infarction. All the 75 cases were divided into two groups depending on the presence or absence of decompensation with disorders of the water-salt metabolism. Despite the duration and pattern of its course, myocardial infarction was shown to be always accompanied by a high activity of the HHNS and adrenal cortex, although different variants of its intensity could be distinguished by the studies of the secretory cycle in neurosecretory nuclei. When infarction was complicated by cardiac decompensation, there developed the state of hypervasopressinism constantly accompanied by hyperthrophy of the glomerular zone of the adrenal cortex producing aldosteron and by an increased concentration of intracellular sodium.