Four patients with acute myocardial infarction (MI) complicating double rupture; interventricular septum and ventricular free wall ruptures, were studied. All patients had histories of hypertension, and pre-infarction angina pectoris of short duration less than 8 days without previous MI. The sites of infarction were anteroseptal in 2 patients and inferoposterior in the other 2. Only one case was complicated with mild pump failure (Killip class II). Blood pressure was adequately controlled after the onset of MI in all patients. Interventricular septal rupture occurred between 2 and 10 days after the onset of MI. Free wall rupture occurred between 2 and 22 days after MI. Types of free wall ruptures were oozing in 2 patients and blow-out in the other 2. Surgical repair was performed in 2 patients with the oozing type rupture, who however died soon after surgery. The autopsy findings were as follows: 3 patients had left ventricular free wall ruptures and one had right ventricular free wall rupture. One of the patients with left ventricular free wall rupture showed a secondary rupture of a pseudo-ventricular aneurysm. Postmortem coronary angiograms revealed 3 patients with single-vessel disease and one patient with double-vessel disease, indicating that coronary arterial lesions and complicated heart failure were not severe in these 4 patients.(ABSTRACT TRUNCATED AT 250 WORDS)