Objective: To evaluate the effectiveness of a web-based protocol, ModerateDrinking.com (MD; "www.moderatedrinking.com") combined with use of the online resources of Moderation Management (MM; "www.moderation.org") as opposed to the use of the online resources of MM alone. Method: We randomly assigned 80 problem drinkers to either the experimental or control group with follow-ups at 3, 6, and 12 months. Results: Seventy-five participants (94%) had outcome data at 1 or more follow-up points, and 59 participants (73%) were assessed at all 3 follow-ups. Comparing baseline measures to the average outcomes at follow-ups indicated a significant overall reduction in both groups in alcohol-related problems and consumption variables. Compared with the control group, the experimental group had better outcomes on percent days abstinent. There was an interaction between intensity of drinking at baseline and treatment in determining outcomes assessing drinking. Less heavy drinkers in the experimental group had better outcomes on log mean blood alcohol content (BAC) per drinking day compared with the control group. Heavier drinkers did not differentially benefit from the MD program on this measure. Mixed model analyses in general corroborated these outcomes. Conclusion: The outcome data provide partial evidence for the effectiveness of the MD web application combined with MM, compared with the effectiveness of the resources available online at MM by themselves. (Contains 5 figures and 2 tables.)