A cross-sectional epidemiological study of a representative sample of high-school students was carried out in Paris in 1992 to evaluate smoking behaviour. Among the 4 872 students, 21% smoked on a regular basis (22.8% of girls versus 19.1% of boys). Factors influencing smoking behaviour included smoking in the parents (especially the mother) and siblings and information on smoking received in elementary school. Education on smoking should be encouraged and provided repeatedly.