Time of onset of supraventricular tachyarrhythmia in relation to alcohol consumption. It is widely believed but has never been proved that idiopathic supraventricular tachyarrhythmias beginning during or after weekends or winter holidays are frequently alcohol-related ("holiday heart" syndrome). The time of arrhythmia onset was therefore studied in relation to self-reported ethanol consumption and results of a screening test for alcoholism (CAGE questionnaire) in 289 patients aged less than 65 years admitted for supraventricular tachyarrhythmias. There were 102 patients having an etiologically idiopathic arrhythmia with a known time of onset. Among them, but not among those with disease-related arrhythmias, patients with arrhythmic episodes beginning on Saturdays or on Sundays were more often chronic alcohol abusers (9 of 19, 47%) than either patients with episodes beginning from Mondays through Fridays (18 of 83, 22%; p = 0.040) or control subjects from the out-of-hospital population (8 of 66, 12%; p = 0.002). In multivariate analysis, the time of arrhythmia onset was related to the CAGE response (G2 = 6.0, p = 0.014) but not to the most recent ethanol use. However, the increased frequency of problem drinkers among patients with weekend-onset idiopathic arrhythmias was only relative, and resulted from a decreased number of abstainers and non-problem drinkers. No conspicuous clustering of alcohol-related arrhythmias was seen after New Year's or May Day. Thus, although the present study confirms an association between heavy drinking and idiopathic arrhythmias beginning during weekends, it shows that the question may be of a relative rather than an absolute overrepresentation. The term holiday heart may also be somewhat misleading since no postholiday accumulation of alcohol-related arrhythmias was found. 