Seven patients with mobile right heart thrombi, 4 floating and 3 pediculated, were recensed between 1985 and 1990. Two patients were admitted for congestive cardiac failure (Group I) and 5 patients for pulmonary embolism (Group II). Both patients in Group I were treated with heparin without complications. In one case, the size of the thrombus decreased in 10 days whereas, in the second case, it disappeared within 8 days. In Group II, the first patient underwent successful thrombectomy. The other four patients were given thrombolytic therapy (UK = 2, rt-PA = 2) associated with appropriate doses of heparin. In the two patients given UK (3M units the first day followed by 1.2 M units per day for 4 days) the thrombus disappeared in the first 48 hours of treatment. One patient had a recurrent pulmonary embolism after 2 hours' treatment; both patients had a fall in haemoglobin of 3 cg/ml at the second day. The second patient died at the 5th day. In the two patients treated by rt-PA (100 mg/7 hours) the thrombus disappeared within 4 hours of starting therapy. One patient had a probable recurrent pulmonary embolism. Both patients had a fall in haemoglobin of 3 cg/ml at the 2nd day of treatment. Right heart thrombi are rare (168 cases in the literature of which 111 were mobile). The prognosis seems to be related to echocardiographic appearances: mortality of mural thrombi is about 4% compared with 50% in mobile thrombi. Very mobile "worm-like" masses are therapeutic emergencies because of the risk of embolism (about 68%).(ABSTRACT TRUNCATED AT 250 WORDS)