Systematic transthoracic echocardiography in all cases of pulmonary embolism may demonstrate right heart thrombi. The results of this monocentric series of 28 consecutive cases observed between 1987 and 1996 were analysed. Twenty-four patients were in NYHA Class IV: thirteen were in cardiogenic shock. Echocardiographic signs of acute cor pulmonale were usually observed: 96.3% of patients had right ventricular dilatation, 85.2% paradoxical interventricular septal motion, 88.9% pulmonary hypertension. The thrombus was typical serpentine (27/28 cases) arising from the lower limb veins. Passage into the left heart chambers through a patent foramen ovale was observed in 3 cases. Pulmonary embolism was confirmed in all cases. This is an extreme therapeutic emergency and 13 patients (46.4%) died despite treatment: surgery (7/16), thrombolysis (2/5), heparin (3/4) or interventional radiology (1/3). After the acute phase, the prognosis was generally good, as demonstrated by the 100% survival rate at 28.6 +/- 25 months. This study confirms the gravity of mobile right heart thrombi in pulmonary embolism. The diagnosis is echocardiographic. No significant difference in mortality was observed between the different therapeutic approaches used in this series. The echocardiographic finding of these thrombi is a traditional indication for emergency surgical embolectomy. Thrombolysis is rapid and readily available and seems to provide promising results alone or before surgery. In patients with contraindications to thrombolysis, interventional radiology or simple heparin therapy may be proposed.