Myocardial lesions occuring in diseases with acute increase of intracranial pressure were investigated. Morphologic alterations in heart muscle in spite of different lengh of surviving and various causes of the death were of similar type. In every case subendocardial haemorrhage could be observed on the septal surface and on the papillary muscle of the left ventricle. Focal intracellular edema, myocytolysis were revealed in 76%, focal necrosis of hypercontractic type developed in 52% of the cases. Cellular infiltration occurred around the alternations observed in 3 cases. It is concluded, that damage to the heart muscle is not caused directly by the increased intracranial pressure or catecholamine mobilisation, but seems to be the consequence of the acute myocardial hypoxia.