Authors experienced six cases of diphtheric myocarditis among 23 cases of diphtheria of the nose, pharynx and larynx at Department of Otolaryngology, Busan National University Hospital for 5 years, 1970 to 1974. It resulted as follows ; Diphtheric myocarditis seemed to start around 6~15 days after clinical symptoms of diphtheria of the nose, pharynx and larynx appeared. The peculiar pattern of electrocardiogram was change of S-T segment and T-wave. The motality was so high percentage of cases (5 of 6).