Objectives : To assess the impacts of implementing case payment system (CPS) to Medical Aid (MA) hemodialysis patients on the frequencies and expenditure of dialysis. Methods : Fifty-eight clinics and 35 tertiary care hospitals were identified as having a minimum of 10 hemodialysis patients for each of the MA and Medical Insurance (MI) programs, who received hemodialysis from the same dialysis facilities for both periods of July 2001 and July 2002. From these facilities, a total of 2,167 MA and 2,928 MI patients were identified as the study subjects. Using electronic claims data, the changes in the total number of monthly treatments and charges for outpatient hemodialysis treatments for each patient after the introduction of the CPS were compared between the MA and MI patients. Multiple regression analyses were performed to examine the independent impact of the CPS on the utilization and expenditure of dialysis treatments among the MA patients. Results : There was a significant decrease in the total charges for the hemodialysis treatments of the MA patients, 3.4% (p<0.05), whereas a significant increase was observed for the MI patients, 2.5% (p<0.05). For both the MA and MI patients, the frequency of the monthly hemodialysis treatments were significantly increased, 5.5 (from 12.1 to 12.7) and 7.8% (from 11.6 to 12.5), for the MA and MI patients, respectively. However, a multivariate regression analysis showed no significant difference in the changes in the total number of monthly hemodialysis treatments between the MA and MI patients after implementation of the CPS. Another regression model, regressing on the changes in the monthly claims of dialysis treatments, showed a significant negative coefficient for the MA ((=-70725, p<0.05). Conclusion : The significant decrease in the total charges for hemodialysis treatments among MA as compared to MI patients suggests that there was a cost reduction in the MA program following the introduction of the CPS.