Some people are adept at using discrete emotion categories (anxious, angry, sad) to capture their felt experience; other people merely communicate how good or bad they feel. We theorized that people who are better at describing their emotions might be less likely to self-medicate with alcohol. During a 3-week period, 106 underage social drinkers used handheld computers to self-monitor alcohol intake. From participants' reported experiences during random prompts, we created an individual difference measure of emotion differentiation. Results from a 30-day timeline follow-back revealed that people with intense negative emotions consumed less alcohol if they were better at describing emotions and less reliant on global descriptions. Results from ecological momentary assessment procedures revealed that people with intense negative emotions prior to drinking episodes consumed less alcohol if they were better at describing emotions. These findings provide support for a novel methodology and dimension for understanding the influence of emotions on substance-use patterns.