Cannabis is the most commonly tried and most widely used illicit psychoactive substance in France. In 2003, among people aged 12 to 75, 4.2 million had used it in the past year, and 850,000 had used it at least ten times in the past month. In 2002, this level of use—ten times in a month—was more common among 17-year-olds (6.8% of girls and 17.7% of boys) than among 18- to 25-year-olds (6.3%) and 26- to 44-year-olds (1.3%). The rise in frequent use among adolescents and young adults, as well as the levels recently reached, raise questions about patterns of use and the consequences of cannabis use. (R.A.)