This study examines whether the number of hours of television watched by young adults is associated with performance on standardized exams and whether any such relationship is causal. Data from the National Longitudinal Survey of Youth, the High School and Beyond survey and the National Education Longitudinal Study all indicate a negative cross-sectional relationship between hours of television viewing and test scores, even after controlling for a variety of socioeconomic characteristics. However, endogeneity bias may underlie this negative relationship. Models that include individual or family fixed effects to partially control for endogeneity suggest that television viewing does not negatively affect performance on standardized exams.