Demonstrating sustained abstinence following adolescent smoking cessation intervention has remained an elusive goal, particularly for adolescents with heavier smoking patterns. The major purpose of this study is to improve smoking cessation rates among adolescent smokers by promoting both intrinsic and extrinsic motivation to change. This randomized clinical trial will use a 2 x 2 between groups factorial design to investigate the separate and combined effects of two primary intervention factors for adolescent smokers (ages 14-19), recruited from school settings, who are low in motivation to change their smoking. The first factor, the Reinforcement Component, contrasts contingency management (CM), in which adolescent smokers will be reinforced for reductions in smoking behavior, to the comparison intervention of noncontingent reinforcement (NR), in which adolescents will receive reinforcers regardless of smoking levels. The second factor, the Psychosocial Component, contrasts motivational enhancement therapy (MET) to the comparison intervention of progressive muscle relaxation (REL) to quit smoking. We hypothesize that the combination of CM and MET will be instrumental in increasing both intrinsic and extrinsic motivation to change smoking behaviors. Efficacy will be determined by randomly assigning adolescent smokers to one of four conditions: (1) CM + MET, (2) CM + REL, (3) NR + MET, or (4) NR + REL. Groups will be compared at 1-, 3-, and 6-month follow-ups periods of self-report and biochemical measures of smoking. The separate and combined effects of MET and CM on changing behaviors related to smoking will be assessed, including percent days abstinent, abstinence duration, and biochemical measures. Mechanisms of change will be explored through examination of potential mediating effects of self-efficacy and motivation to change smoking on outcome. By integrating two behavioral interventions, this work has the potential to reduce smoking rates among heavier smoking adolescents and enhance our understanding of mechanisms of action.