School-based prevention programs are an important component of problem gambling prevention, but empirically effective programs are lacking. Stacked Deck is a set of 5-6 interactive lessons that teach about the history of gambling; the true odds and "house edge"; gambling fallacies; signs, risk factors, and causes of problem gambling; and skills for good decision making and problem solving. An overriding theme of the program is to approach life as a "smart gambler" by determining the odds and weighing the pros versus cons of your actions. A total of 949 grade 9-12 students in 10 schools throughout southern Alberta received the program and completed baseline and follow-up measures. These students were compared to 291 students in 4 control schools. Four months after receiving the program, students in the intervention group had significantly more negative attitudes toward gambling, improved knowledge about gambling and problem gambling, improved resistance to gambling fallacies, improved decision making and problem solving, decreased gambling frequency, and decreased rates of problem gambling. There was no change in involvement in high risk activities or money lost gambling. These results indicate that Stacked Deck is a promising curriculum for the prevention of problem gambling.