Purpose: The -509C/T polymorphism of the transforming growth factor (TGF)-β1 gene has been associated with asthma and atopy. We evaluate whether TGF-β1 promoter polymorphism (-509C/T) is associated with the asthma phenotype and the development of atopy in Korean children. Methods: We enrolled 278 patients with atopic asthma, 54 non-atopic asthma and 248 healthy children. They underwent through pulmonary function tests and methacholine challenge tests with their eosinophil counts of blood, total serum IgE levels and serum eosinophil cationic protein levels. TGF-β1 promoter polymorphism was genotyped using PCR-restriction fragment length polymorphism (RFLP) assays. Results: No significant difference was observed in allele and genotype frequencies of TGF-β1 -509C/T polymorphism between the patients with atopic asthma or non-atopic asthma and control subjects. Any pulmonary function or atopic variables were not associated with this polymorphism. Furthermore, we showed that -509C/T polymorphism was not associated with bronchial hyperresponsiveness. Conclusion: These results suggest that the -509C/T polymorphism of the TGF-β1 promoter gene may not be associated with bronchial asthma or atopic variables in Korean children.