This study reports the results of an intervention to stop the illegal sale of cigarettes to minors. Sixty-two of 120 stores in Erie County, New York, were randomly selected to receive in the mail an informational packet requesting their help in stopping the illegal sale of tobacco to minors. The packet included a letter to the store manager citing the law prohibiting the sale of tobacco products to minors and requesting their assistance in observing the law; a supply of warning signs; and a tip sheet designed to assist store managers in educating their employees about the law. Two weeks after the mailing, stores in the study were visited by study teenagers aged 14 to 16 who attempted to purchase cigarettes. The intervention resulted in an increased number of stores posting warning signs, but had no effect on deterring the sale of cigarettes to minors. Minors purchased cigarettes in 77% of stores that received the special mailing and in 86% of nonintervention stores. Warning signs were visible in 40% of stores that received the special mailing and in none of the nonintervention stores. The findings from this study suggest that a merchant education program to increase awareness of the law and posting of warning signs is not sufficient to discourage the sale of tobacco products to minors.