INTRODUCTION AND AIMS: Young adults' weekend alcohol consumption is characterised by heavy episodic drinking (HED) with low alcohol use in between. This study investigates whether consuming a lower or higher number of drinks than usual on a given evening predicts consumption the following evening. DESIGN AND METHODS: In French-speaking Switzerland, 115 young adults (57% female, mean age = 23.2) answered questionnaires on their cellphones six times every Thursday, Friday and Saturday evening over five consecutive weeks. Multilevel models with group-mean centering were used to analyse 462 evening pairs. RESULTS: Although the sample average number of drinks consumed tended to increase from Thursday [Mmen (SD) = 3.6 (5.0); Mwomen (SD) = 2.9(4.2)] to Saturday [Mmen (SD) = 7.4( 7.1); Mwomen (SD) = 5.2(5.6)], substantial day-to-day variations were observed within individuals. Variations from the usual consumption (i.e. higher or lower number of drinks than usual) on the first day had a significant inverse impact on amounts consumed the following day (unstandardised regression coefficient (B) = -0.27, P < 0.01). This effect was more marked for evening pairs including HED (B = -0.44, P < 0.001). Men and heavy drinkers were less subject to day-to-day variations than women and usually moderate drinkers. DISCUSSION AND CONCLUSIONS: The inverse relationship might result from adverse consequences experienced after HED or an intentional reduction in alcohol consumption in anticipation of a heavy drinking session the next day. Event-specific prevention is needed for women and usually light or moderate drinkers as their more distinct consumption peaks put them at greater risk, particularly of accidents and injuries.