In order to explore the utilization and medical cost of patients with different insurance coverage in group practice centers, we collected patient data in three centers from September 1, 1987 to February 28, 1988. We classified the payments as self-payment,partial-reimbursement and total-reimbursement. There were 42,234 visits by 8,111 patients. The average frequency of visits within 6 months was 6.1 in total-reimbursement patients, 5.2 in partial-reimbursement patients and 2.6 in self-payment patients. We found that the frequency of visits increased with age in patients with total-reimbursement and partial-reimbursement. On the other hand, the frequency decreased after the age of 65 in patients with self-payment; whether it was related to the economic problems of the elderly needs further study. The highest medical cost per visit was NT$. 343 in total reimbursement patients, followed by NT$. 281 in partial-reimbursement patients. The lowest cost was NT$. 208 in self-payment patients. Yet, the highest ratio of total drug cost by total medical cost per visit was 73.7% in partial-reimbursement patients followed by 63.6% in total-reimbursement patients. The lowest ratio was 56.7% in self-payment patients. Although the partial-reimbursement system could not decrease the ratio of total drug cost by total medical cost per visit, it would be beneficial in group practice centers to decrease the patients' visits and the medical cost per visit. Therefore, this system should be executed in the future.