Three surveys are reviewed, each designed for a different purpose and each covering a different population. This paper addresses the issues of coverage, sample design, and weighting In three national surveys: Monitoring the Future (MTF), the National Household Survey on Drug Abuse (NHSDA), and the Youth Risk Behavior Survey (YRBS). Philosophically, the three studies are very different, since they take very different approaches to the problem of measurement. Two of these surveys use samples of schools while the other survey (NHSDA) is a survey of households. NHSDA Is also aimed at the entire population, whereas the two school based surveys deal only with teens. YRBS has both a national sample base and separate samples/studies for states and local areas. This review deals only with issues related to estimates for the teenage population that is targeted by the three surveys, and only for the nationally based samples. Subnational estimates are considered as part of this review.