Concurrent use of alcohol and cigarettes among adolescents is a serious public health issue. Trends in concurrent use of alcohol and cigarettes were determined using data from three comparable large statewide samples of 7-12th-grade students in New York State, from surveys conducted in 1983, 1990, and 1994. The prevalence of use of alcohol and cigarettes decreased from 1983 (23%) to 1990 (19%), and increased by 1994 (22%). Logistic regression analysis showed that these trends are highly significant, and that the probability of use of alcohol and cigarettes is higher for females than males, increases with age, and is lower for most ethnic minorities than for Whites. In the 1990s, Blacks, Hispanics, and Asians increased in their probability of concurrent use more than did Whites. Users of both alcohol and cigarettes are at increased risk of personal and social problems, as well as increased risk of delinquency. Drinking and smoking show synergistic effects on illicit drug use and drug problems.