This study examined the prevalence, age of initiation, and pattern of substance use among 1,617 Mexican-American and non-Hispanic White high school students residing within the same geographic community. Ethnic differences were present for current smoking, having used alcohol in the past month, "heavy drinking" per occasion, and ever used marijuana. Age of initiation of substance use and the pattern of use was similar for the two ethnic groups. Future research needs to determine if the progression of initiation represents a sequence of initiation, identify factors that influence movement along the sequence, and determine if there are ethnic differences.