A large national database (U. S. Centers for Disease Control and Prevention [CDC], 2001) was analyzed for age, sex, race/ethnicity and television viewing among American adolescents aged 12-18 years. Body Mass Indices (BMI) were calculated from self-reported height and weight. Ninety-fifth percentile and above was classified as obese; [less than]95th percentile was classified as non-obese. After controlling for age, sex and race, odds ratios were calculated for obesity and hours/day of television viewing on an average school day. Five or more hours of television viewing on an average school day roughly doubles the risk of obesity. This holds for both males and females. Moreover, these data show a linear trend toward obesity as daily television viewing increases. These data confirm--at the national level--the earlier regional studies linking television viewing to obesity. Health educators may now consider television viewing as a significant risk factor for adolescent obesity. (Contains 4 tables and 2 figures.)