A prospective birth cohort study in 312 pregnant women from Northern Manhattan investigated whether environmental tobacco smoke (ETS) and a gene-environment interaction may predispose to risk of AD in children. ETS was assessed by questionnaire and cord blood cotinine levels. Parental reports of AD were collected by questionnaire over 3 years. The cohort was stratified by ethnicity into Dominican and African American groups. At age 3 years there was an increase in AD risk for Dominicans with polymorphisms in GSTT-02 and GSTP1 (p<0.05 for both). Exposure to prenatal ETS increased the risk of AD in Dominican children with a val/val genotype at GSTP1 (relative risk=3.3; p<0.03). GST polymorphism alone or combined ...