A histochemical, cytophotometric and morphometric study of hypothalamic microcirculatory vessels was conducted in 2 samples: 50 sudden cardiac deaths from coronary heart disease and 50 cardiac deaths from clinical myocardial infarction that were not sudden. Non-sudden cardiac death was associated with moderate venous hyperemia and high postcapillary alkaline phosphatase activity. In cases of sudden coronary death, three patterns of microcirculatory changes were identified that differed with respect to the quantity of functionally-inactive capillaries, the markedness of edema in hypothalamic tissues and hypothalamic content of vascular mast cells. Relationships between the said differences and different dates of death are discussed.