The purpose of this study is twofold: 1) to evaluate the effects of a smoking cessation clinic (Project EX) on changing motivation to quit smoking, and 2) to assess differences in quit rates based on these changes in motivation. Student smokers in 18 continuation high schools in the Los Angeles county area were invited to participate in a tobacco cessation clinic designed to enhance motivation to quit tobacco use. The 18 schools were randomly assigned to one of three conditions. Compared to students in the control group, students who participated in the program conditions were more likely to express higher motivation to quit tobacco use. Higher motivation was also significantly related to higher quit rates. Motivation to quit as defined by constituents of the energy/direction model of motivation appears to be a plausible mediator of cessation program effects.