[Evaluation of a schoolbased intervention to promote smokefree areas].

Objective: To determine the effect of an intervention in secondary schools on visible tobacco use, the prevalence and intensity of smoking, and the attitudes and behaviors of teachers and students.

Methods: We performed a quasiexperimental study in 18 public secondary schools that carried out the program and in 18 that did not (control group). Information was obtained on visible tobacco use and the number of ashtrays and smokefree posters through direct observation.