Background Very few studies have examined the role of school, household and family contexts on youth smoking in middle-income countries.

Methods This work describes smoking exposure among 59 992 high school students who took part in the Brazilian Survey of School Health and investigates contextual factors associated to regular smoking, defined as smoking cigarettes at least 1 day in past 30 days. Explaining variables were grouped into: sociodemographic characteristics, school context, household context and family rapport. Variables independently associated with smoking in each context were identified by multiple logistic regression.

Results 53% were female, 89% were aged 13–15 years. 24% had already experimented cigarettes, 50% before the age of 12 years. Prevalence of regular smoking was 6.3% (95% CI 5.87 to 6.74), with no sex variation. Smoking was not associated with mother's education or index of household assets. In the multivariable analysis, studying at private school, possibility of purchasing cigarettes at school and skipping classes without parent's consent increased the chance of smoking. In the household context, living with both parents was negatively associated with smoking, while having smoking parents and exposure to other people's smoking was positively related to smoking. In the family rapport, parental unawareness of what the adolescent was doing increased smoking, but having meals with the mother one or more days per week and parents' negative reactions to adolescent smoking were protective.

Conclusion Results reinforce the roles of school, household and family contexts on youth' smoking behaviours and help to adjust public health policies aimed at adolescents.