IMPORTANCE Despite progress against tobacco sales to minors, retailers continue to violate state and federal laws and supply adolescent smokers with tobacco products. Government-sanctioned surveys underestimate the extent of the problem, and retailer associations use these data to block stricter enforcement policies.OBJECTIVES To assess the validity of the US federal retailer violation rate (RVR) as an estimate of the proportion of retailers that sell tobacco to minors and to investigate what proportion always or almost always sells vs refuses to sell cigarettes to minors.