One third of women continue to smoke during early pregnancy, although evidence for detrimental effects of in utero smoke exposure on fetal growth and development are rising. A number of epidemiologic studies have shown that prenatal exposure to environmental smoke is an independent risk factor for poor lung function, wheezing, and the development of (possibly nonatopic) asthma. Epidemiologic data on the effect on development of allergic sensitization are inconclusive, since in most studies no clear separation is made between pre- and postnatal exposure. However, studies that included prenatal smoke exposure showed no effect on sensitization. Aberrant development of the fetal lung structure, as shown in experimental models, may underlie the increased risk for poor lung function and asthma development. Recently, we showed that maternal smoking during pregnancy decreased expression of genes that are involved in lung development in lungs of neonatal mice. In addition, maternal smoking during pregnancy increased airway remodeling in adult mice offspring. Future experimental studies may reveal whether lung developmental changes may additionally underlie susceptibility to the apparent adult-onset disease chronic obstructive pulmonary disease.