OBJECTIVE: To study the polarization and immune regulation of TH cells in patients with bronchial asthma. METHODS: Thirty-eight hospitalized children with bronchial asthma (ranging from 4-12 years old) and 29 age-matched healthy children (Control group) were enrolled in this study. Serum IL-2 and IFN-γ levels were detected using ELISA. The percentage of TH1 and TH2 cells was detected by intracellular staining. RESULTS: The serum levels of IL-2 (15.94± 3.07 μg/L) and IFN-γ (487.2±43.6 pg/mL ) in asthmatic patients were significantly lower than those in the Control group (24.73±4.37 μg/L and 654.07±14.64 pg/mL respectively; P<0.01). The percentage of TH1 in asthmatic patients decreased significantly compared with that in the Control group [(11.24±2.43)% vs (16.67±2.73)%; P<0.01 ]; in contrast, the percentage of TH2 increased compared with that in the Control group [(19.85 ± 4.46)% vs (16.08±6.17)% ; P< 0.05 ]. CONCLUSIONS: The serum levels of IL-2 and IFN-γ, and the number of TH1 cells decreased in asthmatic patients. The decreased number of TH1 cells and the ratio of TH1/TH2 suggest an abnormal polarization of TH1 and TH2 cells. The changes may be associated with the inhibition of cellular immune function in asthmatic patients.