Abstract: Adolescent alcohol and nicotine abuse is common, but its neurodevelopmental consequences remain unclear. This laboratory utilized adolescent rodent models to assess the hypothesis that adolescents are highly susceptible to the effects of alcohol and nicotine. Rats were exposed to ethanol for 10-14 days using an intermittent vapor inhalation paradigm. Rats were continuously exposed to nicotine for 5 days using Nicoderm CQ™ transdermal patches. Alcohol or nicotine exposure altered neurobehavioral function when assessed after 3-7 weeks of abstinence. Alcohol-induced changes include increased electroencephalographic (EEG) frequency, decreased amplitude of the cortical N1 and hippocampal P3 event-related potential (ERP) components, enhanced anxiety-like behavior, and enhanced depressive-like behavior. Nicotine-induced changes include decreased slow-wave cortical EEG power, increased cortical N1 ERP amplitude, decreased motor activity, and increased anxiety-like behavior. These findings support the hypothesis that adolescents are uniquely susceptible to the effects of chronic alcohol and nicotine exposure.