This study examines the risk for alcohol and other drug (AOD) problems resulting from alcohol plus marijuana use compared to alcohol-only use. Data are from telephone interviews with 1113 randomly selected college students attending two large urban universities in the southwestern United States. Alcohol and marijuana users (dual users) were more likely to be younger and report a higher mean number of drinks per occasion and experiencing all AOD problems studied compared to alcohol-only users. Multivariate logistic regression analysis findings reveal the relationship between dual-substance use and increased risk for AOD problems remained after controlling for demographics and alcohol use behaviors. Such problems include greater odds of legal problems and riding with or being an intoxicated driver. College students using alcohol and marijuana are at much higher risk for AOD problems than are students who use alcohol only, even when heavy drinking is taken into account. (Contains 3 tables.)