Computer games may be an effective tool for teaching health-related knowledge and skills. This study evaluates the effect of a novel computer game about the glycemic index (GI) on knowledge, self-efficacy, and behavioral intention for adopting a lower GI diet. A pretest-posttest, nonequivalent control group design was employed. Students aged 18-30 years (n = 65) either completed the GI computer game or reviewed US Department of Agriculture's MyPyramid Web site regarding healthy eating guidelines. Participants completed a GI knowledge test, a self-efficacy instrument, and a questionnaire that assessed intentions to choose lower GI food choices. The computer game group showed greater gains than the control group in knowledge (P < .001) and self-efficacy scores (P < .01). Scores regarding behavioral intention also were significantly higher (P < .001) for the game group. A game-based approach may be effective in facilitating the adoption of lower GI food choices.