Background: Minnesota and Massachusetts require parental permission, for persons younger than 16 or 18 years of age, respectively, for indoor tanning. Objectives: This report examines business practices and characteristics associated with sales of indoor tanning to underage girls. Methods: Fifteen-year-old girls tried to purchase an ultraviolet tanning session in 200 indoor tanning businesses in the Minneapolis-St Paul and Boston areas without parental consent. Business characteristics were recorded. Later, businesses were interviewed by telephone about their facilities and practices. Results: Eighty-one percent of businesses sold a session to an underaged buyer on at least one of two tries. Illegal purchases did not differ by state. Businesses least likely to sell were larger, dedicated to indoor tanning, required employee certification, and had a minimum age of sale for their business. However, businesses in each of these categories still sold tanning sessions to underaged adolescents at 44% to 62% of the visits. Employees who requested parental consent or age identification almost never sold a session. Limitations: Businesses in Minnesota and Massachusetts only were included. Conclusion: Minnesota and Massachusetts laws specifying a minimum age of sale for indoor tanning are ineffective.