Thirty-four patients with severe scorpion sting were reviewed and pertinent data related to the cardiovascular system such as hypertension, peripheral vascular collapse, congestive heart failure or pulmonary edema were analyzed. The electrocardiograms of 28 patients were reviewed; 14 patients showed "early myocardial infarction-like" pattern. The urinary catecholamine metabolites were investigated in 12 patients with scorpion sting. Vanylmandelic acid was elevated in seven patients and the total free epinephrine and norepinephrine in eight. Six of these 12 patients displayed the electrocardiographic "myocardial infarction-like" pattern. Nine patients died and the pathologic lesions of the myocardium were reviewed in seven. The causes of heart failure, pulmonary edema and the causes of the morphologic changes of the myocardium are discussed. It was concluded from our observations, as well from recent experimental studies, that the cardiovascular manifestations of the venom and morphologic abnormalities are related to the level of circulating catecholamines elicited by a direct effect of scorpion venom on the sympathetic system. These studies suggest that adrenergetic blockers should be used in the treatment of the cardiovascular manifestations of scorpion sting.