OBJECTIVE To compare the serological characters of an outbreak of hepatitis E and evaluate sensitivity and specificity of anti-HEV E2-IgM. METHODS The sera collected from the employees of an outbreak unit were detected for anti-HEV E2-IgM and IgG, and the serum samples from a neighboring department were used as control. The results detected with anti-HEV E2-IgM, IgG and Genelab anti-HEV IgM, IgG in some samples were compared. RESULTS The positive rate of anti-HEV E2-IgM in the control group was 0.11%. The results between the positive and the negative samples can be distinguished easily. The specificity of anti-HEV E2-IgM is about 99.89%. The positive rate of anti-HEV E2-IgM in outbreak stricken population was 8.66%, significantly higher than that in the control group (P < 0.001). The results from HEV patients' serial samples in the outbreak unit showed that the anti-HEV E2-IgM titer was high 30-60 days after the infected and then declined clearly. The positivity seemed unrelated to neither sex nor age. Among the 115 positive to anti-HEV E2-IgM, 27 were negative to Genelab anti-HEV IgG, the fact indicated a rather high risk of misdiagnosis of about 23.48%. In the 179 randomized samples of the control group, the positive rate of Genelabs anti-HEV IgG was about 11.17%. In 110 samples for the positive anti-HEV E2-IgM, the positive ratio of Genelabs anti-HEV IgG was about 76.36%, and that of Genelabs anti-HEV IgM only 69.09%. There were 16 samples negative for both Genelabs anti-HEV IgG and IgM. The ratio of the difference between the Genelabs anti-HEV IgG and IgM was about 25.45%. CONCLUSIONS The specificity of anti-HEV E2-IgM was about 99%, and false positive rate was low. The sensitivity of anti-HEV E2-IgM in acute hepatitis E infection was 25%-30% higher than that of Genelabs anti-HEV IgM,IgG. The infected persons in the outbreak unit can be preferably distinguished from the non-infected persons by anti-HEV E2-IgM. Anti-HEV E2-IgM can image the characters of the outbreak of HEV and played a great role in the control of outbreak and in the early diagnosis for hepatitis E.