To provide information that may promote more effective cancer prevention, we identified factors associated with regular smoking among adolescents in Lyon, France. School grades where these factors began to influence regular smoking were also identified. Seven consecutive cross-sectional anonymous surveys were conducted in three public schools, beginning in grade 6ème (average age 11.5 years) in 1993 and ending in grade Terminale (average age 17.4 years) in 1999. All classes in each respective grade were surveyed, with 3650 completed questionnaires for all years combined. Prevalence of current regular smoking is presented according to school grade for 17 variables identified as significantly related to regular smoking in a multivariate logistic regression analysis. Important factors associated with regular smoking were identified as early as grade 6ème and included not viewing the taking care of one's health as important, not eating breakfast regularly, associating with groups where smoking occurs, having a best friend who smokes, and having a brother and/or sister who smokes. Not regularly reading was first associated with an increased risk of regular smoking in grade 5ème. Not living with both parents, alcohol drinking, episodes of drunkenness, illicit drug use, and sexual relationships were positively associated with regular smoking in the middle and later grades, when these questions were first asked. Not playing sports and not playing with computers were initially associated with an increased risk of regular smoking in grade 3ème.