The aim of this study is to improve understanding of trends in adolescent substance use by comparing them with trends in peer substance use, school problem behavior, parental disapproval of alcohol and drugs, and exposure to school prevention information. These trends were determined using data from three large comparable representative surveys of 7-12th grade students in New York State conducted in 1983, 1990, and 1994. Analysis of variance was used to test the significance of the trends and to identify meaningful differences in trends by demographic subgroups (gender, grace level, and ethnicity). Adolescent alcohol and substance use declined in the 1980s, then increased from 1990 to 1994. Trends in friend's substance use and school problem behavior paralleled the alcohol and other substance use trends, consistent with their being part of the same adolescent problem behavior syndrome. Parental disapproval also followed a trend consistent with the substance use trends, i.e., parental disapproval increased in the 1980s but then decreased in the 1990s. However, the trend in school prevention influences did not parallel these substance use trends: student exposure to school primary prevention programs continued to increase from 1990 to 1994. Use of alcohol, cigarettes, marijuana, and other illicit drugs from 1990 to 1994, increased fastest among the younger students, despite increased school prevention exposure. Other factors must be sought as possible explanations of the increasing alcohol and substance use among adolescents.