To evaluate the effectiveness of the Not-On-Tobacco Program. Methods: Forty-four high schools implemented the program (n=241 students), with 27 comparison schools (n=251 students). Students reported smoking in the last 7 and 30 days at baseline and follow-up. Results: Those in the program had an increased likelihood of reporting 30-day abstinence at end of program (OR = 4.2) but not at 6 or 12 months. For 7-day abstinence there was no significant difference for any time point. Conclusions: In this effectiveness evaluation the N-O-T Program increased quitting during the program, but the effects were not present at 6 or 12 months.