Objective To observe the effects of Yukouning on immunologic function in recurrent aphthous ulcer (RAU) patients with brimming heat of heart and spleen (BHHS type).Methods The study was composed of 30 patients with RAU (BHHS type) and 30 healthy individuals.All patients with RAU (BHHS type) were divided into levomisole group and Yukouning group (n =15).Patients of levomisole group were give 50 mg of levomisole,bid,lasted two days.Patients of Yukouning group were give Yukouning decoction.The changes of the class of T-cells and the levels of immunoglobulins (IgA,IgG,IgM) and complement (C3,C4) in different groups were tested by flow cytometry (FCM) and single immunodiffusion method.Results The levels of CD8+,IgG,IgA,C3 and C4 in RAU (BHHS type) patients increased significantly as compared with those in healthy group (P ＜ 0.05).The level of CD4+ and the ratio of CD4+/CD8+ decreased significantly as compared with those in healthy group (P ＜0.05).Furthermore,the levels of CD8+,IgG,IgA,C3 and C4 in RAU (BHHS type) patients decreased significantly after different drug treatment,respectively (P ＜ 0.05).At the same time,the level of CD8+ and the ratio of CD4+ / CD8+ increased significantly after different drug treatment,respectively (P ＜ 0.05).But all the above-mentioned indexes had no significant differences between the two drug groups (P ＞ 0.05).After 1-year follow-up,the effective rate (both 93.3％) had no significant difference between the two groups (P ＞ 0.05).Conclusion Imbalance of immune function is correlated with RAU (BHHS type).Yukouning plays a therapeutic role by regulating cellular and humoral immunity in RAU (BHHS type) patients.