The possible negative therapeutic interaction between aspirin and angiotensin converting enzyme inhibitors arose from the conclusions of several experimental studies and retrospective analysis of large scale mortality trials with converting enzyme inhibitors. Some experimental results show inhibition of the vasodilatation of converting enzyme inhibitors, increase in pulmonary pressures, vascular resistances and blood pressure, and degradation of renal function and exercise capacity. However, other studies did not confirm these results. In large scale therapeutic trials, some retrospective analyses, but not all of them, have shown less benefit on morbi-mortality of converting enzyme inhibitors in patients on aspirin. The differences between the doses of aspirin, the type and dosage of the converting enzyme inhibitors and neuro-hormonal activation of the patients could explain the discordant results. The results of randomised trials are awaited but, in the meantime, it is logical to propose small doses of aspirin (< or = 100 mg/day) for patients with cardiac failure and atherosclerosis and to avoid the association in all the other patients.