Purpose: Kawasaki disease (KD) is an acute febrile illness of infants and young children that is characterized by a systemic vasculitis, especially involving the coronary arteries. Although, sometimes, subclinical myocarditis is combined in KD, symptomatic myocarditis is extremely uncommon. We report a 7 year old boy who developed hypotension and decreased left ventricular systolic function (EF 40%) in the acute phase of KD. Case: A 7 year old boy (height 115 cm, body weight 20 kg) was admitted because of 2 days of persistent fever and left cervical lymphadenopathy (white blood cell count 17,870 /mm 3 , C reactive protein 23.6 mg/dL). Conjunctiva injection and lip redness developed on the 4th day of illness, and hypotension and tachycardia (SBP 59/DBP 29 mmHg, HR 153/bpm) were combined. The echocardiography revealed a decreased ejection fraction (EF) (40%) without chamber dilatation and normal coronary artery size (LM 1.9mm, z score=-1.3, RCA 2.3mm, z score=0.4). The level of N terminal pro BNP was 28,000 pg/mL. With a diagnosis of KD with myocarditis, he was initially treated with inotropics and intravenous immunoglobulin (2 g/kg). Without clinical improvement in spite of initial treatment, A change of coronary arterial size (LM 2.9mm, z score=1.2, RCA 3.1mm, z score=2.3) was developed and decreased LV systolic function (EF 45%) and fever were persisted. Then, he was given 3 daily pulses of intravenous methylprednisolone followed by tapering doses of oral prednisolone. He showed prompt clinical recovery after pulse therapy of intravenous methylprednisolone (SBP 95/DBP 49 mmHg, HR 98/bpm). Although EF was improved (59%), coronary arterial dilatation was progressed (LM 3.4mm, z score=2.4 RCA 5.5mm, z score=7.9). Conclusions: The present case serves to highlight the fact that methylprednisolone should be considered as the priority in children with KD who have symptomatic myocarditis during the acute stage.