24 cases of cardiac rupture (CR) (12%) were found in 200 necropsies of patients who died from acute myocardial infarction (AMI). Examination of the various factors that may affect the onset of this complication showed that age, sex, the site of AMI, the presence of coronary thrombosis, the association of persistent arterial hypertension, diabetes mellitus or previous angina syndrome and anticoagulant and corticosteroid treatment are insignificant. On the other hand, previous myocardial infarction would appear to reduce incidence considerably. CR was much more frequent in the first 3-4 days after onset of AMI and never occurred more than 21 days after. An important premonitory sign is persistent precordial pain in the absence of pericardial friction. Cardiokinetic therapy was used in 70% of the CR cases examined here. Over the past decade, the frequency of CR secondary to AMI has risen appreciably and it is hypothesised that this increase may have been influenced by the readiness with which cardiokinetics are employed now during AMI, often in very high doses. Particularly in the case of patients at high CR risk, it is considered that cardiokinetic therapy should only be employed in cases of clear cardiac insufficiency, in small, fragmented doses and after diuretics and vasodilators have proved ineffective. Such patients can also usefully be transferred to specialist wards for emergency surgery or preventive infarctectomy.