The current report presents the results of a study that attempted to validate the Transtheoretical Model of Change (TMC) as a model for youth gambling behaviour change. The study used a cross-sectional design to collect data from Ontario high school students in the Niagara Region (grades 9-13; N = 5,524). Approval was requested and obtained from Niagara Region school boards, with eight schools across the region agreeing to participate. High schools were located in both rural and urban areas. The questionnaire completed by students included measures that examined their current gambling behaviour, perceptions of the positive and negative aspects of gambling, temptation to gamble, stages of change, and processes of change. The present study builds upon our previous research in 2001/2002 where we first developed the TMC subscales (stages of change, temptation to gamble, decisional balance inventory for gambling, and processes of change) to reflect youth gambling behaviour. The present study attempts to validate these newly developed TMC subscales in a community sample of youth. Since most clinicians use the TMC model to guide their interventions, it is our hope that the validated scales can be used for youth in treatment for gambling problems. As well, it may be that these scales can be used for prevention, as they may suggest how and when to effectively introduce risk reduction and brief intervention strategies aimed at reducing youth problem gambling. The results from this study are intended to provide clinicians and researchers with additional information about the differences between youth who gamble responsibly and those who are at-risk for developing a gambling problem or gambling problematically. These results may be subsequently used to guide the development of education, prevention, and treatment interventions, and may suggest how and when to effectively introduce risk reduction and brief intervention strategies aimed at reducing youth problem gambling.