Accessibility to medical facilities and personnels has been known as one of important determinants of medical care utilization. This study attempted to identify the effects of medical accessibility in terms of geographical distance and occupational opportunity to the medical utilizations. Two-year-experiences of Yonsei University Health Insurance Cooperatives were used as the sources of data. Out patient utilization patterns of 713 members sampled from 4,352 members of Health Insurance Cooperatives were analyzed in order to identify the effects of medical accessibilities. Findings: 1 Average clinic visit rate of Yonsei Health Insurance is 1.66 per person per year. 2. The utilization rates of geographically more accessible group were 33% higher than that of less accessible group. 3. No marked difference in clinic visit rate were observed between medical and non-medical personnel and their family members. 4. Clinic visit rates among occupationally accessible group were slightly higher than those of less accessible. The utilization rate was more sensitively changed by the insurance policy changes in occupationally accessible group.