This paper explores the influence of social factors and school factors on cannabis use among Ontario high school students. The data are derived from a survey of students conducted by the Addiction Research Foundation in 1987. Multiple classification analysis was used to examine the relationship between the two groups of factors and cannabis use. Results of the analysis indicate that social factors are more highly predictive of cannabis use than are school factors. A theoretical framework specifying the influence of social and school factors on cannabis use needs to be developed and tested in order to understand this relationship more clearly.