In this article, the authors present an adolescent counseling intervention used by the California Smokers' Helpline and test in the largest randomized trials to date. In this study, more than 1,400 teen clients were randomly assigned to an intervention group or a control group. Participants in the intervention group received telephone counseling in addition to written cessation materials, whereas participants in the control group received written cessation materials only. Preliminary analysis revealed that significantly more clients in the telephone counseling group than in the control group quit and remained abstinent for 6 months (Zhu, 2003). The results of this study show that the counseling protocol increased the 6-month prolonged abstinence rate for teens. This is a notable result given the challenging task of helping teens quit smoking and the shortage of rigorously tested interventions that have yielded statistically significant effects (McDonald et al., 2003; Mermelstein, 2003). The study addresses the society's approach to adolescent cessation counseling. The study also provides an overview of the theoretical constructs that underlie the protocol; a detailed description of the protocol itself, with special attention to developmental issues that shape the counseling intervention; and a discussion of counselor training for protocol implementation.