Structural and functional neuroimaging studies indicate that heavy alcohol use during adolescence may be neurotoxic to the brain. This chapter reviews the neuroimaging findings in cross-sectional and longitudinal studies of adolescent heavy alcohol users. These youth exhibit reductions in prefrontal, hippocampal, and cerebellar brain volume, decreased frontoparietal, and increased frontolimbic white matter integrity, as well as alterations in blood oxygen level-dependent response during working memory, inhibitory control, verbal encoding, decision making, and reward processing-some of which appear to differ between males and females. Although some exist, additional longitudinal studies will significantly advance addiction medicine by aiding prevention scientists and treatment providers to develop neurobiologically informed ways of strengthening neural networks prior to and after the onset of heavy alcohol use, thereby promoting healthy cognitive functioning across the adolescent period.