Excerpt from the Baromètre Santé survey conducted among 4,115 young people aged 12 to 19. This chapter analyzes the links between alcohol, tobacco, and cannabis use. 26.6% of young people have tried all three substances at least once; this figure rises to 40% among 19-year-olds. Alcohol is the most commonly tried substance. Experimentation with alcohol and, especially, tobacco increases the risk of experimenting with cannabis. One in five young people aged 15 to 19 regularly uses one or more of these substances; among them, one in two has smoked cannabis at least ten times in the past twelve months. Family structure and socioeconomic status are protective or aggravating factors for all of these forms of use.