We have compared the prevalence of asthma, bronchial hyperresponsiveness (BHR), and atopy in relation to parental smoking in children aged 7 to 13 years. Information on the presence of asthma was obtained from a questionnaire, BHR was assessed by a methacholine challenge test, and atopy was defined as a positive response to a skin prick test. A complete history of the parents' smoking habits during their children's life, including prenatal smoking habits, was recorded. The prevalence of maternal smoking increased from 37.9% during pregnancy to 45.3% at the cross-sectional survey. None of the outcomes was significantly related to paternal smoking, whereas postnatal maternal smoking was positively associated with asthma (odds ratio [OR] = 2.8; 95% confidence interval [CI], 1.3 to 6.1). A negative association between prenatal maternal smoking and atopy was found (OR = 0.6; 95% CI, 0.3 to 0.9). We found no significant association between BHR and parental smoking. Our results indicate that postnatal maternal smoking increases the prevalence of asthma in the offspring without inducing BHR.