This study is the first to examine adolescent cigarette report stability over 10 years. Six waves of data were utilized from the National Longitudinal Survey of Youth. This study examined internal/logical consistency and external consistency. Report stability was higher for lifetime use reports than the age of onset reports. Wave-by-wave differences revealed stability increased across time, with one-third denying use in the first two wave comparisons but dropping to 20% by the last comparison. Overall, report agreement was higher for females, older adolescents, and non-Hispanic/non-black youths. Implications regarding misclassification of users for prevention programs and measurement issues are discussed. (Contains 5 tables.)