The beginning of college is a period in which increased alcohol use often coincides with greater involvement in romantic relationships. Existing literature yields inconsistent findings regarding the influence of relationship types on drinking behavior, perhaps because these studies have not accounted for recent changes in the way college students engage in dating/sexual relationships. The present study sought to address this issue using a longitudinal study design by examining the effects of both relationship type and sexual activity on heavy episodic drinking (HED) among 1,847 college students over the course of the first 3 semesters of college. Results indicated that the effects of relationship type depended on whether an individual was sexually active. Nondating but sexually active students reported rates of HED comparable to students who defined themselves as casual daters. Conversely, nondating students who were not sexually active reported drinking behavior similar to those involved in exclusive relationships. Further, transitions between low- and high-risk relationship/sexual activity types were associated with corresponding changes in HED. Transitioning into a high-risk relationship was associated with significant increases in levels of HED, whereas transitioning into a low-risk relationship was associated with significant decreases in HED. Together, results indicate that engaging in nonexclusive dating or casual sexual relationships may play an important role in the development of problematic patterns of alcohol use during the early college years. These findings have potentially important implications both for future research and for prevention and intervention efforts targeting high-risk college drinkers.