The role of ischaemia in post-infarct patients with ventricular tachyarrhythmias is not firmly established. Using coronary angiography, 82 post-infarct patients with sustained ventricular tachycardia or fibrillation were subclassified into three groups. Fourteen patients (17%) had significant coronary artery disease, suggesting that ischaemia was the primary cause (group A). In 13 patients (16%) ischaemia was considered a coexistent factor (group B). In 55 patients (67%) ischaemia did not play a role (group C). The 1-year cumulative arrhythmia-free rate was 100%, 75%, 68% and the 2-year arrhythmia-free rate 100%, 56%, 52% for groups A, B and C, respectively. Using life-table analysis, group A had the most favourable long-term outcome in relation to arrhythmia recurrence. Outcomes of groups B and C were comparable. In a univariate analysis, arrhythmia recurrence was determined by the arrhythmogenic role of ischaemia, the left ventricular ejection fraction and the time from the old infarct to the index arrhythmia. In the absence of arrhythmic events in group A, multivariate analysis of groups B and C identified depressed ejection fractions (RR 0.69, CI 0.49-0.98) and a prolonged time interval from the last infarct (> 5 years, RR 2.53, CI 1.12-5.75) as independent predictors for arrhythmia recurrence. The present approach helps in the identification of post-infarct patients with ventricular tachycardia and fibrillation, who benefit from stand-alone anti-ischaemic therapy. If ischaemia does not play a major arrhythmogenic role, prognosis depends on the left ventricular ejection fraction and on the age of the previous infarct.(ABSTRACT TRUNCATED AT 250 WORDS)