We have observed clinically 57 cases of diphtheria, admitted to Dept. of Pediatrics and E. N. T. of College of Medicine, Busan National University during a period of past 4 years from Jan. 1973 to Dec. 1976. The following results were obtained from this observation: 1. The yearly prevalence rate seemed not to be reduced throughout 4 years. 2. The seasonal incidence was highest from Oct. to next Feb when 77.5% of cases was de-veloped. Most of cases (82.5%) was below the age 8 years with the sex ratio of male to female, 1.5:1. 3. About one half of cases gad been resided in the rural area. 4. Concerning the degree of the immunization status of diphtheria, 48.3% of cases was never taken, 17.5% unknown, 33.4% inadequate, and 5.3% was adequate. 5. The sites of occurence of dephtheria were pharynx (33.3%) larynx (47.4%) and both (19.3%) 6. 77.2% of cases was found diphtheria organism, which was detected on smear (63.2%) and culture (52.6%) individually. 7. The chief clinical symptoms and signs on admission were dyspnea (77.2%) pseudomemb-rane (77.2%) prostration (75.4%) fever (72.0%) hoarseness (54.4%) cough (50.9%) and the like in order of frequency. 8. Anemia was found in 77.2% leukocytosis in 84.2% of cases. 9. 54.5% of cases had complications, of which myocarditis (22.4%) pneumonia (21.0%)bull neck (14.0%) nephritis (12.2%) and nerve palsy (10.5%) were developed. 10. The onest of myocarditis was the 3th-8th day of depheheria and the most common abnormal ECG finding was the changes of S-T segment and T wave. 11. The morality rate was 12.3% of the total cases (45.5% of mixed type the and 7.4% of laryngeal type were expired). The causes of death were myocarditis (its mortality rate, 46. 1%) and paralysis of diapgragm.