Objective: Alcohol is theorized to be motivated by desires to regulate negative affect and/or to enhance positive affect. We tested the association between momentary affect and alcohol use in the daily lives of college students, hypothesizing that alcohol use would be more likely to follow increases in positive affect and that alcohol use would not be strongly associated with negative affect. Method: Using two ecological momentary assessment (EMA) studies consisting of two prompts per day for 28 days, we used multilevel hurdle models to test for lagged associations between positive and negative affect and alcohol use. There were 108 participants (60.19%; mean age = 20.20, SD=1.69) in EMA study 1 and 268 participants (60.03%women, mean age = 20.22, SD=1.96) in EMA study 2. To provide context for the affect-alcohol associations, we collected data on whether participants drank alone or with others at each drinking occasion and the drinking motives of participants using the Drinking Motives Questionnaire. Results: Alcohol use was more likely to occur following increases in positive affect. No significant associations emerged between fluctuations in negative affect and alcohol use. This pattern of findings was observed across both ecological momentary assessment studies. The majority of alcohol use occurred in social contexts. Conclusions: College students who report primarily social and enhancement motives for drinking and who seldom drink alone are more likely to drink following increases in positive affect.