Adolescent smokers screened for a nicotine replacement treatment trial: Correlates of eligibility and enrollment We describe and evaluate the screening process for enrolling adolescent smokers into the randomized clinical trial of nicotine replacement therapy (NRT). Adolescent smokers obtained the recruitment call-in number (1-800-NO-SMOKE) via media and other advertisements. Trained recruitment staff collected information using an internally-developed, targeted telephone screening interview, which was used to determine pre-eligibility for the clinical trial. Correlates of qualification and of study enrollment were determined. Among 1347 adolescents screened, 24.4% (329/1347) were eligible to participate in the trial. Light smoking (39.1%) and lack of parental support (14.8%) were the biggest contributors to ineligibility. Eligible adolescents were more likely to be female (66.9% vs. 58.2%, p=0.0052) and more likely to be European American (63.5% vs. 52.2%, p=0.0003). The higher rates of ineligibility for African Americans and boys were partially explained by lower FTND scores. Of those eligible to participate in the trial, 48.3% (159/329) enrolled. Results underscore the need for screening instruments that are measurement-invariant across ethnicities and gender, and enrollment strategies that maximize inclusion of eligible participants. Ethnoracial differences among adolescent dependent smokers were also explored. Variations in nicotine metabolism are thought to contribute to differences in cigarette consumption between African Americans and Caucasian adult smokers. To investigate the potential mechanism of previously documented lower smoking rates among African American adolescent smokers seeking cessation treatment, we measured nicotine metabolite ratios as markers of the metabolic disposition of nicotine, which is generally considered to be under the influence of cytochrome P450 (CYP) 2A6. Plasma ratios of trans-3?-hydroxycotinine (3HC) to cotinine (COT) were examined in ninety-two cessation treatment seeking adolescents (mean age 15.2 SD 1.3, 69% female, 31% African American, mean Fagerstrom Test for Nicotine Dependence (FTND) 6.5, SD 1.6, mean years smoked 2.6 SD 1.6). Groups were similar in age, gender distribution and mean FTND score. Analysis using independent t-tests revealed significantly lower number of cigarettes per day (CPD) (15.1 SD 7.6 vs. 19.6 SD 8.0, p=0.013) and nicotine metabolite ratios (0.27 SD 0.15 vs. 0.35 SD 0.16, p=0.026) in African American compared to Caucasian adolescent smokers. Consistent with metabolic variation, mean COT/CPD ratio was significantly higher in African American compared to Caucasian adolescents. Results remained statistically significant after controlling for menthol brand smoking. These findings are consistent with those found among adult smokers and provide a putative mechanism for reported ethnoracial differences in adolescent cigarette consumption. Our results underscore the need for measures independent of consumption for determining degree of nicotine dependence and treatment selection across ethnicities, even among youths.