Although the "holiday heart syndrome," highlighted by rhythm disturbances after acute alcohol ingestion, is well known, the potential arrhythmogenic effects of alcohol have not been studied. Fourteen patients (two with congestive cardiomyopathy) with a history of rhythm disturbances and alcohol consumption were studied electrophysiologically. One patient had nonsustained ventricular tachycardia, one had nonsustained atrial fibrillation, one had paired ventricular responses, and the remainder had no response to the extrastimulus technique. After 90 mL of 80-proof whiskey, 10 of the 14 patients developed sustained or nonsustained atrial or ventricular tachyarrhythmias. Significant prolongation of His-ventricular conduction was seen after alcohol intake; this was noteworthy as one of the patients had previously shown Mobitz II atrioventricular block after acute alcohol consumption. Alcohol in modest doses has the potential to produce rhythm disturbances in patients with a history of chronic alcohol consumption and heart disease.