In children with a high-risk genotype (HR/RR) for EPHX1 H139R, exposure to paternal tobacco smoke during pregnancy was associated with increased risk of childhood brain tumors (OR = 1.78; 95% CI: 0.81, 3.91), whereas there was little observed association in children with a low-risk genotype (HH) (OR = 0.83; 95% CI: 0.45, 1.54). The gene discussed is EPHX1; the disease is brain neoplasm.