The study analyses 58 consecutive (1971-1981) cases with haemodynamically significant pulmonary embolism (PE) treated in a coronary unit. The diagnosis was confirmed either by pulmonary angiography or a combination of scintigraphy with haemodynamic examination, or by autopsy. In 75.8% of cases there were present predisposing factors. A combination of sudden dyspnoea with venous thrombosis or with recurrent thrombophlebitis in the anamnesis was present in 59.3% acute cor pulmonale in 1/3 of the patients. The chest X-ray showed in 83.9% of the patients one of the following signs: pulmonary infarction, oligaemia, elevation of the diaphragm, enlargement of the hili, amputation of the hili, pleural effusion. In 62.7% of the patients, PE could be diagnosed on the basis of the ECG. Most patients had elevated pulmonary artery pressure, with a worse prognosis in patients exhibiting a pressure higher than 40 mmHg. For suspecting the presence of haemodynamically significant PE, it is in most patients sufficient to rely on the anamnesis and the results of physical, ECG and X-ray examination. The diagnosis should be confirmed by scintigraphy or angiography and haemodynamic examination.