Objective-Well-documented challenges have hampered both intervention development and research in teen smoking cessation. Addressing these challenges, the Hutchinson Study of High School Smoking (HS Study), the largest group-randomized trial in adolescent smoking cessation to date, incorporates several design innovations to investigate the effect of a counselor-initiated, individually tailored telephone counseling smoking cessation intervention for older adolescents. This paper presents and discusses these innovative design features, and baseline findings on the resulting study population.Method-The trial used a population-based survey to proactively identify and recruit all high school juniors who had smoked in the past month-potentially expanding intervention reach to all smokers, even those who smoked less than daily and those not motivated to quit. For ethical and intervention reasons, some nonsmokers were enrolled in the intervention, also. Other important design features included the random allocation of schools into experimental conditions (intervention vs. nointervention control) and a multi-wave design.Results & Conclusion-The design innovations address problems and challenges identified in adolescent smoking cessation literature. The heterogeneous baseline characteristics of the study population, well-balanced between the two arms, have three significant implications: They (1) demonstrate the effectiveness of the trial's design features, (2) highlight several intervention-related issues, and (3) provide assurance that the trial's evaluation of intervention effectiveness will be unbiased.