Our hypothesis was that children with mutations in genes coding for glutathione S-transferases (GST) have worse asthma outcomes compared with children with active type genotype. Data were collected in five populations. The rs1695 single nucleotide polymorphism (GSTP1) was determined in all cohorts (3692 children) and GSTM1 and GSTT1 null genotype were determined in three cohorts (2362 children). GSTT1 null (but not other genotypes) was associated with a minor increased risk for asthma attack and there were no significant associations between GST genotypes and asthma severity. Interactions between GST genotypes and SHS exposure or asthma severity with the study outcomes were nonsignificant. We find no convincing evidence that the GST genotypes studied are related to asthma outcomes.