The blood levels of catecholamines, serotonin, histamine and acetylcholine were studied in 17 patients with severe and moderate coronary shock. The blood level of the above vasoactive substances varied widely, and no clear regularity was noted in the changes of the content of the catecholamines, histamine, serotonin and acetylcholine. A relatively higher (on the average) level of noradrenaline was noted in severe shock, in contrast to the moderate cases, as well as a relatively low level of noradrenaline and acetylcholine in the blood of patients with a full atrioventricular block and bradycardia. In studying the vasoactive substances dynamically similar, phase-like fluctuations of the blood level of histamine and serotonin were noted in some patients. In a few cases similar, often phase-like, changes were also noted in the blood content of noradrenaline and acetylcholine