Background
: To prepare the basic educational data for primary care physicain who work to maintain and enhance the health of people in community. The authors carried on disease frequency analysis in medical Insurance in Korea.

Methods : To clarify the frequency of reasons which made people to use health delivery system in Korea, the authors has made descriptive study with 113,244,548 cases of actual visits to the health delivery system of Korean medical insurance from January 1st to December 31st of the year 1991. The objectives of this study are 100,000 random sampling cases of medical visits among 113,244,548 actual cases of those.

Results : 1. Females(54.5%) have made more frequent medical visits to the health care system than males(45.5%) 2. The frequent diagnoses are acute upper respiratory infection of multiple or unspecified site, acute bronchitis&bronchiolitis, acute nasopharyngitis, acute tonsilitis and acute pharyngitis in order. 3. There is a significant dissimilarity of disease pattern between the in-parient and out-patient group. Among the upper twenty frequent disease, only five disease are concord between the two groups. 4. There are higher prevalence of respiratory infections in the first and second decade, genitourinary infections in the third and forth decade, gastrointestinal diseases in the fifth and sixth decade and then hypertension above the seventh decade.

Conclusion : 53.3% of all visits to health care system were upper twenty frequent diseases. The people who have acute, transient problems made more frequent visits to the primary health care system than to the secondary or tertiary of those. It is needed to encourge primary health care system.