In the current study, 3 participants with a history of problem gambling were exposed to computerized slot machine play consisting of outcomes that depicted wins, losses, and near misses (2 out of 3 identical slot machine symbols). Participants were asked to rate each type of outcome in terms of its closeness to a win on a scale of 1 to 10 before and after a brief acceptance and commitment therapy intervention. The intervention, which was specifically designed to address one type of rule following in gamblers called the "near-miss effect," was delivered via a Microsoft PowerPoint presentation within a brief experimental session. Results were evaluated within a multiple-baseline-across-participants design and demonstrated a decrease in the near-miss effect after intervention. Implications for treatment of problem gambling are discussed. (Contains 1 table and 2 figures.)