Purpose: Mycoplasma pneumoniae is an important cause of community acquired pneumonia and may cause extra-pulmonary manifestations but a few investigation for its liver involvement had been done. The object of this study is to know its recent hepatic manifestations and their effect on prognosis. Methods: I collected the clinical informations of 174 mycoplasma pneumonia patients who had been admitted at the Department of Pediatrics , Yongin Severance Hospital, Yongin, Korea from January 2008 to December 2010. Hepatic involvement cases were defined with serum transaminase level[ 40 IU/mL and over in serum asparate aminotransferase(AST) or 45 IU/ mL and over in alanine aminotransferase(ALT)]. Their clinical characteristics, demographics, laboratory findings, biochemical profiles, treatment outcomes were analysed and compared with no hepatic involvement cases. Results: There were fifty-five cases(31.6%) with serum transaminase elevation among mycoplasma pneumonia children. Thirty cases of them (54.5%) were observed at 2010 year. Their age was 3.3± 2.4 years old and twenty-seven cases(49.1%) were younger than 3 years old. Almost half of them(47.3%) were found in spring. Male to female ratio was 1:1.2. Their nonrespiratory symptoms and sign were loss of appetite(81.8%), nausea(58.2%), vomiting(40.0%), hepatomegaly(9.1%). Almost all of them(90.1%) showed AST elevation only. Their AST and ALT level were 63.7± 56.9 IU/L and 37.8± 68.9 IU/L, respectively. Forty-three cases(78.5%) were discharged within 5 days. The transaminase elevation of 48 cases(87.3%) was recovered within ten days. Patients with hepatic manifestation were significantly younger(P=0.004), more frequent in spring(P=0.039) and not longer admission duration than patients without it. They were comparable with each other in terms of fever, white blood cell counts, erythrocyte sedimentation rate, C-reactive protein elevation. Conclusion: It is frequently observed at very young age and in spring. Although it does not impact on prognosis, it should be kept in mind because its prevalence is not uncommon.