The Ontario Student Drug Use Survey's target population is Ontario students enrolled in grades 7, 9, 11, and 13 in the regular and separate school systems that use a more rigorous stratified (grade by region) single-stage cluster sample. The 1995 survey, conducted in February through April 1995, surveyed 3,870 students from 20 school boards, 137 schools, and 233 classes. Seventy-five percent of eligible students participated in the survey. The data-gathering instrument used was a self- administered, anonymous questionnaire completed in class groups in 30-to 40-minute sessions. A random half sample were questioned on treatment experience and need for treatment (n = 1,936). Based on a sample of students who reported alcohol use within the last 12 months (n = 1,191), the study determined problems related to alcohol use and experience of treatment or need for treatment. Among students with two or more alcohol-related problems, 2.7 percent had been in a treatment program because of their alcohol or drug use in the last year, and 5.4 percent felt they needed treatment, but 31 percent wished they could drink less alcohol. Among students with two or more drug-related problems, 8.4 percent had been in a treatment program, 12.2 percent felt they needed treatment, and 19.8 percent wished that they could use drugs less than they do now. Implications of the findings for effective approaches to reduce the problems and consequences of alcohol and drug use among youth are discussed. 2 tables and 20 references