Since 1977, alcohol and drug use among Ontario students has been studied every 2 years. To examine the patterns of alcohol and other drug use among Ontario students in 1983, a randomized sample of 5,835 students, representing grades 5, 7, 9, 11, and 13, from four geographical regions, completed an anonymous questionnaire. An analysis of the results showed that, as in previous surveys, the most prevalently used drug was alcohol, followed by tobacco and cannabis (such as marihuana). Most types of drugs, except for glue and other solvents, were more popular among older students (except grade 13). Also, illicit drug use, with the exception of cannabis, was still relatively infrequent among users. Only non-medical stimulant use increased between the two periods. The 1983 survey, in contrast to 1981, indicated that a slightly greater number of substances were more commonly used among males than females. This reflected significant increases in the use of six substances among males (glue, other solvents, medical barbiturates and tranquillizers, non-medical stimulants, and hallucinogens other than LSD or PCP). In contrast, no increase in drug use was found among females. (More specific drug use patterns by age, sex, grade, and geographic regions are also described in this report. Changes in usage patterns between 1981 and 1983 are analyzed, and trends in use since 1977 and 1979 are presented.) (Author/BL)