The aim was to evaluate the effectiveness of a web-based brief alcohol intervention ‘What Do You Drink’ (WDYD) among heavy drinking students at 1- and 6-month post-intervention. Additionally, it was investigated whether certain subgroups would benefit more than others from the WDYD intervention. A two-arm parallel group randomized controlled trial was conducted online in the Netherlands in 2010-2011. Inclusion criteria were: (1) being between 18- and 24-year old, (2) reporting heavy drinking in the past 6 months, (3) being motivated to change alcohol consumption, (4) having access to the Internet and (5) giving informed consent. Participants (N = 913) were randomized to the experimental (WDYD intervention) or control condition (no intervention). Measures were heavy drinking, frequency of binge drinking and weekly alcohol consumption. Analyses according to the intention-to-treat principle revealed no significant main intervention effects in reducing the alcohol measures at the follow-up assessments. Secondary analyses revealed that gender, freshmen and fraternity or sorority membership did not moderate the effect of the WDYD intervention at both follow-ups. Readiness to change, problem drinking and carnival participation moderated intervention effects such that contemplators, those with severe symptoms of alcohol abuse or dependence, and those who participated in carnival benefited more than others from the WDYD intervention regarding weekly alcohol consumption at 1-month follow-up. The WDYD intervention was not effective in reducing the alcohol measures among heavy drinking students at 1- and 6-month postintervention. However, there is preliminary evidence that the WDYD intervention is effective in lowering drinking levels for subgroups of heavy drinking students in the short term.