A 16-year-old girl with myocarditis and hepatitis in the course of mycoplasma pneumoniae infection was reported. She had fever and coughed for ten days prior to admission. At the time of admission infiltrations of the left lower lung field were revealed on the chest X-ray films. The ESR was elevated and CRP+6. There were no leukocytosis and anemia, but S-GOT, S-GPT and LDH were moderately increased. On the 11th day of admission VPC in bigeminy appeared and the third sound was heard. Subsequently biphastic and inverted T waves in leads V2 and V3 and flattening of T waves in leads II and aVF appeared. At the same time, the cardiac shadow was enlarged. Antibody titer to mycoplasma pneumoniae increased to more than 1:640 two weeks after admission and then it decreased gradually. The cold agglutinin test was 1:64 on the 8th day of the disease and then it became normal. ASO, antibodies to DNA and immunoglobulins were normal; ANA, Coombs test and LE test were negative. The abnormal ECG-findings were normalized three months later.