The risk of interference with anaesthesia and the risk of decompensation of the disease must be considered for each drug. Beta-blockers reduce the body's capacity to react to hypovolaemia, but they are beneficial by limiting the response to nociceptive stimuli and by reducing the incidence of myocardial ischaemia. Treatment should therefore be continued. Interferences with the dihydropyridine class of calcium channel blockers on peripheral vasomotor activity are moderate and additive. These agents are well tolerated and can be continued until the operation. Verapamil and diltiazem have a chronotropic and negative inotropic effect which is additive with that of anaesthetics. Administration of these drugs before the operation does not raise any major problems, nor does their discontinuation. Angiotensin-converting enzyme (ACE) inhibitors, used in hypertension and heart failure, considerably reduce the tolerance of factors modifying the blood pressure equilibrium, especially hypovolaemia or haemorrhage. In practice, ACE inhibitors carry a risk of intraoperative hypotension, requiring the use of vasopressor amines to maintain blood pressure. Continuation of treatment has only minimal advantages, regardless of the indication and there is no risk of rebound effect after stopping treatment. The treatment washout period depends on the duration of action of the product. However, discontinuation of treatment is never imperative, regardless of the context.