Objective To study the detection of IgM antibodies against coxsackie B viruses and their significance of etiology and diagnosis for patients with myocarditis. Method seventy pediatric patients were divided into three groups: 20 cases of myocarditis, 25 cases of suspect myocarditis and 25 cases of the control group. The presence of CBV - IgM and CBV - IgG was detected by indirect ELISA. Results The test revealed 11 of 20 (55% ) CBV - IgM opitives in the myocarditis group, 11 of 25 (44% ) CBV- IgM positives in the indirect myocarditis group and 11 of 25 (44% ) CBVIgM positives in the control group. There were no significant differences among the three groups (x2 = 1. 1286, P > 0. 05). Conclusions The presence of CBV-IgM positive by indirect ELISA indicates that the patient is infected by CBV. It Is an etiologic evidence of patients with myocarditis. But it is not a clinical diagnostic evidence of patients with myocarditis.