Study of the type of premedication used in aorto-coronary bypass surgery involved 60 clinical cases of patients operated upon in the department of Professor GALEY (Henri Mondor Hospital, Creteil). The choice of drugs used showed the important role of tranquilisers and anxiolytics: diazepam, dipotassium chlorazepate, to which, in the majority of cases, were added an antihistamine: promethazine and a parasympatholytic: atropine. No accidents or complications were seen during the pre-anaesthetic period, and above all during the induction of anaesthesia in these patients, more than half of whom were in major cardiovascular decompensation. This would appear to confirm the efficacy of the drugs chosen for the premedication of these patients.