This study was designed to investigate factors relating to fiscal deficit for regional health insurance. The financial statements for the fiscal year 1990 of nationwide 254 regional medical insurance societies were analyzed. Important findings are summarized below: 1. There were differences in the main reason fur the financial deficit among regions when deficit and surplus societies were compared by regions. The total revenue per enrollee, especially revenue from the premium contribution of a deficit society was significantly smaller than that of a surplus society in large cities and counties. On the other hand, the total expenditure per enrollee of a deficit society was larger than that of a surplus society in small cities. 2. Both low premium rate at the beginning of health insurance program and less effort to increase the premium rate were main factors for the smaller revenue from the contribution of a deficit society in large cities and counties. 3. Larger expenditures per covered person of a deficit society in small cities were explained with larger medical expenditures especially for out-patients services rather than larger administrative expenses. 4. A regression analysis showed that utilization rates in out-patient services were significantly associated with income and numbers of total medical care institution per capita within a region where a health insurance society located. Also expenses paid by insurer per visit were associated with the proportion of utilization for tertiary care hospitals as well as the proportion of utilization of public health centers.