Abstract
This study describes the content and functions of applications that promote illicit drug use (apps) in smartphone app stores (i.e., Apple App Store and Google Play), and measures the overall growth of these apps over a three-month period. Moreover, we investigate whether the app stores' regulation systems are exposing children and adolescents around the world to these apps. We identify a large and expanding pro-illicit-substances repository within smartphone app stores, which should raise concerns over public health. The content rating criteria used by app stores are insufficient, and government intervention may be necessary to enforce proper standardization of app-rating processes.