Magid HSA, et al. - This study was undertaken to determine if the proximity and density of tobacco retailers near students’ homes were correlated with a higher likelihood of initiating alternative tobacco product (ATP) use over time. Utilizing information from 728 adolescents (13–19 years of age at baseline) living in 191 different neighborhoods and attending 10 different California high schools, longitudinal multilevel and cross-classified random effect models assessed individual-level, neighborhood-level, and school-level risk factors for ATP initiation after 1 year. The sample was predominantly female and was diverse both racially and ethnically. Findings suggested an association of living in neighborhoods with greater tobacco retailer density at baseline with higher odds of ATP initiation, controlling for individual and school factors. Findings suggested that tobacco retailers clustered in the home neighborhood of students may have an environmental impact on the use of ATP by adolescents. Policy efforts to decrease adolescent use of ATP should aim at reducing tobacco retailers' density and limiting the proximity of tobacco retailers to homes and schools for adolescents.