We observed 241 cases of type A hepatitis who were admitted to pediatric department of St. Mary`s Hospital, Cathlic Medial College from Jan. 1,1968 to Dec. 31,1977, and the following results were obtained. 1. Annual incidence was the highest in 1975 and lowest in 1969, but wr observedno significant difference. 2. Seasonal incidence was high in Autumn and Winter, and low in Spring and Summer. 3. Age incidence showed high in 7,8,6 and 5 years of ages in order of frequency. the age group of 3-10 years old occupied 76.3% of total cases. Sex incidence revealed male predominance with the ratio about 1.6:1. 4. The common clinical symptoms on admission were anorexia(68.8%), abdominal pain and discomfortness(66.0%), nausea and vomiting(59.8%), dark urine(53.1%) and fever(30.0). 5. The common physical findings on admission were jaundice(75.1%), hepatomegaly(68.8%), abdominal distension(14.5%) and palpable spleen(8.7%). 6. The hematologic findings on admission(total leukocytes, lymphocyte and ESR) were within normal limitis in the most of the cases. 7. Bilirubinuria was observed in about 65% of the tested cases during the first 2 weeks of the illness and urinary urobilinogen was increased during the first and third week of the illness and decreased during the second work of the illness. 8. In the majority of the cases the serum bilirubin reached peak during the second week of illness and ranged 2~15mg. And by the end of the fourth week of the illness, they returned to lese than 2mg% in the 86.5% of the tasted cases. 9. SG0T and SGPT reached peat during the first week of the illness and decreased to less than 100unit by the end of fourth week of the illness in the most of the tested cases. 10. TTT did not return to normal level in the 70.0% of the tested cases by the end of the fourth week of the illness. 11. The electrophoresis of the serum portein revealed slightly decreased alpha1-globulin and increased gamma-globulin level than normal. 12. Anicteric hepatitis was 37 cases(15.3%) of the total cases. 13. Hepatitis B surface antigen was positive in 3 cases(3.8%) of the 79 tested cases. 14. In the most of the cases, prognosis was excellent but 3 cases complicated hepatic coma and expired.