Abstract: AIM: To explore the role of T lymphocyte subgroup and B lymphocytes in the pathogenesis of viral myocarditis. METHODS: The quantity of CD4+CD45RA+, CD4+CD45RO+ and CD19+ in peripheral blood of viral myocarditis patients was detected using flow cytometry, and cTnI level was measured. Healthy subjects served as controls. RESULTS: The quantity of CD4+CD45RA+, CD4+CD45RO+ and CD19+ in acute patients (<1 month) was significantly different from those in controls (P<0.05). The difference of CD4+CD45RA+ and CD4+CD45RO+ was notable within 1 month (P<0.01; P<0.01). CD4+CD45RO+ decreased in the first week and CD4+CD45RA+ decreased in the second week. The difference of CD4+CD45RA+/CD4+CD45RO+ was significant from 14 to 30 days. The difference of CD19+ was notable from 1-3 months. CD4+CD45RA+/CD4+CD45RO+ cyte ratio imbalance was observed in acute stage. In recovery phase (3-12 months), the quantity of CD4+CD45RA+, CD4+CD45RO+, CD19+ and CD4+CD45RA+/CD4+CD45RO+ cyte ratio in patients was not significantly different from those in controls. CONCLUSIONS: In viral myocarditis patients, T lymphocyte subgroup abnormality and B lymphocyte abnormality play an important role, respectively, in early infection (<1 month) and in later infection (1-3 months). Th1/Th2 cyte ratio imbalance exists in acute stage (<3 months). In recovery phase (3-12 months), T lymphocyte subgroup and B lymphocytes recover gradually.