An epidemiological study on diabetic ketoacidosis (DKA) was done by analysis of 207 cases collected from the medical records of 6 major general hospitals in Seoul area during the period of 5 years between 1979 and 1984. There was female predominance in the occurrence of DKA (male/female ratio, 0.71) in spite of the male predominance in general prevalence of diabetes mellitus (1.80). This female predominance in DKA was most striking in the age group under 40. There was a significant seasonal variation in the occurrence of DKA. DKA occurred most frequently in colder season with the highest peak in December. In July and August, the hottest season in Korea, not even a single case of DKA was recorded in this series. No discernible precipitating factor was found in 39.3% of DKA cases and infections was present as a cause of DKA in 30% of cases. In 27.5%, DKA was the first clinical presentation of diabetes and in the remainders of cases, diabetes was known to be present for average of 6.4 years. Mortality of DKA was 13.2% in this series. As to the socioeconomic status, the education level, the style of living and the duration of diabetes, there were not ascertainable differences between the DKA cases and other diabetic cases. The prospective epidemiological study of diabetic population in Korea, especially in female group, would be necessary for elucidation of the characteristics of DKA in Koreans such as the female predominance and the seasonal difference of the occurrence.