Surveillance of drug use among American Indian adolescents: patterns over 25 years. 
To examine the trends in drug use among American Indian adolescents attending schools on, or near, Indian reservations in the United States, to provide comparisons with non-Indian youth, and to discuss implications for prevention.  Reliable and valid school administered drug use surveys have been given every year for 25 years (1975-2000) to representative samples of Indian youth living on reservations, yielding a continuous record of trends in drug use.  Comparisons are made with non-Indian youth with data from the Monitoring the Future project.  Data were analyzed to obtain measures of lifetime prevalence ("ever tried a drug"), use in the last 30 days, and proportions at high risk and at moderate risk from their drug use.  Comparisons utilized difference in proportion tests.  From 1975 to 2000, reservation Indian youth show elevated levels of drug use for most illicit drugs compared with non-Indian youth.  Despite higher levels of use, the trends showing increases and decreases in use over time mirror those shown by non-Indian youth.  Indian youth who use drugs can be divided into moderate and high levels of use.  The number of youth in the moderate category varies over time whereas the number in the high category remains relatively constant.  There is a clear need for intensive efforts to reduce the levels of drug use among Indian youth.  Although interventions must be tailored to the social and cultural milieu of Indian reservations, the rates of use vary over time in the same pattern as seen for non-Indian youth.  Further, interventions must address the differing characteristics of high and moderate risk users of drugs.