Epidemiological data indicate a robust association between smoking and alcohol use. However, a critical question that is less resolved is the extent to which the smoking event takes place during the time of alcohol consumption. The present study used data from an 8-week prospective web-based study of college student smokers to examine daily associations between smoking and alcohol use, using measures of both likelihood and level of use. Findings indicated that consumption of alcohol and smoking covaried on a daily basis per person. In addition, consistent with the idea of smoking as a social activity for college students, light smokers were more likely than heavier smokers to smoke while drinking and to smoke more cigarettes while drinking. Smoking behavior among light smokers may be influenced by external social contextual cues, in contrast to heavier smokers who may be more affected by internal cues. Implications of findings for prevention work suggest the importance of targeting social situations in which smoking and drinking co-occur.