This study tested associations between positive and negative affect and heavy drinking in 734 college students who completed daily diaries in 14-day bursts once per semester over 7 semesters (98 days per person). Three-level multilevel models tested whether affect and heavy drinking were linked across days, semesters, and persons. Higher daily, between-semester, and between-person positive affect were each associated with greater odds of heavy drinking on weekdays and on weekend days. A significant interaction with semester in college showed that the association between daily positive affect and heavy drinking on weekend days became stronger over time. That is, heavy drinking on a weekend day with higher positive affect was more likely in l...