OBJECTIVE: To evaluate the influence of a history of arterial hypertension and the level of pretreatment blood pressure on the efficacy of the angiotensin converting enzyme (ACE) inhibitor trandolapril on mortality and morbidity in patients with acute myocardial infarction (AMI) and left ventricular dysfunction. METHODS: Data from the Trandolapril Cardiac Event study, in which 1749 patients with an enzyme verified AMI and echocardiographic evidence of left ventricular dysfunction were randomized in a double-blind manner to treatment with trandolapril or placebo, were retrospectively analysed. Follow up time was 24-50 months (mean 26 months). RESULTS: Four hundred patients (23%) had a history of arterial hypertension. A total of 173 (43%) patients with a history of hypertension died during follow up versus 500 (37%) patients in the normotensive group. Treatment with trandolapril in the hypertensive individuals was associated with a reduction in the relative risk of death to 0.59 (95% confidence interval 0.44-0.80), versus 0.85 (0.72-1.02) in the normotensive individuals. The significant reduction in mortality in hypertensive individuals persisted after multivariate analysis controlling for a broad spectrum of potential confounders. Also, benefit from ACE inhibition increased with increasing blood pressure at the time of randomization. Significant interactions between benefit from ACE inhibition and hypertension history, and systolic and diastolic blood pressure were found. CONCLUSION: ACE inhibition after AMI complicated by left ventricular dysfunction may be of particular importance in patients with a history of arterial hypertension or a relatively high pretreatment blood pressure. However, further investigations are necessary to establish the clinical impact of these results.