Two brief treatments for problem gambling were compared with a waiting-list control in a randomized trial. Eighty-four percent of participants (N = 102) reported a significant reduction in gambling over a 12-month follow-up period. Participants who received a motivational enhancement telephone intervention and a self-help workbook in the mail, but not those who received the workbook only, had better outcomes than participants in a 1-month waiting-list control. Participants who received the motivational interview and workbook showed better outcomes than those receiving the workbook only at 3- and 6-month follow-ups. At the 12-month follow-up, the advantage of the motivational interview and workbook condition was found only for participants with less severe gambling problems. Overall, these results support the effectiveness of a brief telephone and mail-based treatment for problem gambling.