Results indicated a relationship between geographical origin (as a measure of ethnicity) and alcohol and drug use. Higher levels of alcohol, cannabis, and other illicit drug use, as well as violent behavior and delinquency was observed among detained youth than among dropout youth. Higher levels of these behaviors were found among Toronto youth in comparison to Amsterdam and Philadelphia youth. The findings suggest that differences in substance use and other forms of deviant behavior within ethnic groups may be attributed to differences between countries and samples rather than differences between “western” and “non-western” youth. The research was part of the Drugs, Alcohol and Violence International (DAVI) study in which 1,120 detained and dropout youth between the ages of 14 and 17 years were interviewed at 3 sites: Philadelphia, Toronto, and Amsterdam. Interviews focused on four measures of ethnicity--country of birth, language spoken, ethnic identity, and geographical origin--as well as demographic characteristics, violent behavior, violent victimization, engagement in delinquency, and past year substance abuse. Ordinary least squares regression models were used to analyze the impact of the different measures of ethnicity on violence, delinquency, and substance use. Tables, figure, references