Typical symptoms of acute myocardial infarction led to admission of a 66-year-old female. Creatine kinase (CK) was 720 U/l on admission and together with CK-MB of 108 U/l fitted the clinical picture. The ECG showed complete left bundle branch block. The patient died a few hours later in cardiac failure. Massive hypercalcaemia of 6.2 mmol/l and hyperphosphataemia of 1.6 mmol/l suggested acute primary hyperparathyroidism already clinically which later could be verified by a parathormone level of more than 100 000 ng/l ("C-terminal assay"). At necropsy chief cell adenoma of the epithelial bodies was found, typical changes of primary hyperparathyroidism in the skeleton and kidneys, and disseminated calcifications and fresh necroses of cardiac muscle. The coronaries were normal. This is the first clinical report of fatal acute primary hyperparathyroidism due to hypercalcaemia-induced myocardial necroses.