Although drinking by U.S. adolescents has decreased during the last decade, more than 20 percent of U.S. high-school students continue to drink alcohol before the age of 14 years. This can have adverse effects on their neurodevelopment. Little is known about how the age of alcohol-use onset influences brain development. This is the first study to assess the association between age of adolescent drinking onset and neurocognitive performance, taking into account pre-existing cognitive function.