Adolescence is a critical period for the emergence of clinical problems, such as substance abuse and dependence. Adult studies have demonstrated adverse effects of chronic heavy alcohol use on brain structure and function. However, little research exists regarding how initiation of alcohol use interacts with neurodevelopmental processes that are active in adolescence. Given that a large majority of adolescents initiate alcohol use, a key question is how this initiation disrupts the developmental fine tuning of brain connectivity patterns. We are examining this question through a longitudinal project funded by the National Institute of Alcohol Abuse and Alcoholism and National Institute on Drug Abuse. Our work to date indicates that alcohol use initiation is associated with declines in cortical thickness in the frontal lobe, with deviations in white matter development in posterior cortical regions, and with disrupted white matter connectivity in the striatum and periventricular regions.