Syncope or presyncope related to adverse drug reactions are well-known. On the other hand, little is known about the specific role of different drugs. Over one six year period, 1611 patients were referred in our hospital for syncope or presyncope, including 688 in the cardiology department. Among these patients, 420 were 70 years old or more. The search for an adverse drug reaction was systematic, with the help of the French method for causality of adverse drug reaction: knowledge of "extrinsic" criteria (bibliographical data relating to the drug involved); moreover, score on the basis of "intrinsic", chronological and symptomatic criteria. Seventy five patients (11% of the group with syncope leading to admission in cardiology department) were thus retained: score = I2, "possible adverse drug reaction", for 28 patients (37%); score = I3, "probable adverse drug reaction", for 47 patients (63%). Score I4, "definite adverse drug reaction" was not used since it required the readministration of the drug to prove the iatrogenic effect. Average age was 78 years, with a female majority of 69%. Seventy two patients (96%) had previous cardiovascular disease, 37 (50%) previously experienced syncope or presyncope. In addition to the basic assessment, a Holter recording was performed among 56 patients, finding a drug-induced arrhythmia in three cases. In the majority of the patients (59 patients, 79%), the adverse drug reaction consisted of hypotension, clinically obvious in 49 cases. In ten cases, vasovagal syndrome facilitated by the drugs was diagnosed by a tilt-test. The other side effects were eight rhythm disorders and eight severe metabolic disorders. The treatments were always multiple. The involved drug was a cardiovascular therapy in 66% of the cases. The other drug classes were primarily represented by uroselective alpha 1-adrenergic blocking drugs (12%) and psychotropic ones (22%). Among the cardiovascular treatments, ACE inhibitors and diuretics, generally in association, were involved (59%). This study confirms the role for antihypertensive drugs in iatrogenic syncope, its great frequency in elderly patients but also the responsibility of another drug class less often reported, the uroselective alpha 1-adrenergic blocking drugs.