OBJECTIVE: To observe the TH cell subset function in children with recurrent tonsillitis (RT) at the remission stage and to study the effects of astragalus membranacus (AM) on TH cell subset function. METHODS: The peripheral blood mononuclear cells (PBMC) from 27 children with RT at the remission stage were stimulated with either phytohemagalutinin (PHA) (RT-PHA group) or PHA together with AM (RT-AM group) and were then cultured in vitro for 48 hrs. The samples from 21 healthy children stimulated with PHA were used as the Control group. The levels of interferon-γ(IFN-γ) and interleukin-4 (IL-4) in the supernatants of PBMC were detected using ELISA. RESULTS: The IFN-γ level and the ratio of IFN-γ/ IL-4 in the RT-PHA group were statistically lower than those in the Control group (P<0.01). The level of IFN-γ and the ratio of IFN-γ/IL-4 in the RT-AM group were markedly higher than those in the RT-PHA group (P< 0.01), but were significantly lower than those in the Control group (P<0.05). There were no differences in the IL-4 level among the three groups. CONCLUSIONS: TH1 cell subset dysfunction may exit in RT children at the remission stage, suggesting that TH1 cell subset dysfunction plays an important role in the pathogenesis of RT. AM can improve TH1 cell subset function and therefore shows an important significance in treating RT.