OBJECTIVE: To assess the impacts of implementing case payment system (CPS) to Medical Aid (MA) hemodialysis patients on dialysis frequencies and expenditure. METHODS: Fifty-eight clinics and 35 tertiary care hospitals were identified as having a minimum of 10 hemodialysis patients for each of MA and Medical Insurance (MI) programs, who received hemodialysis from the same dialysis facilities for both of July, 2001 and July, 2002. From these facilities, 2167 MA and 2928 MI patients were identified as study subjects. Using electronic claims data, changes in the total number of monthly treatments and charges for outpatient hemodialysis treatments to each patient after the introduction of the CPS were compared between 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 MA patients. RESULTS: There was significant decrease in total charges of hemodialysis treatments for MA patients by 3.4% (p<0.05), whereas significant increase was observed for MI patients by 2.5% (p<0.05). For both MA and MI patients, the frequency of monthly hemodialysis treatments were significantly increased, 5.5% (from 12.1 to 12.7) and 7.8% (from 11.6 to 12.5) increase for MA and MI patients, respectively. However, a multivariate regression analysis results showed that there was no significant difference in the changes in the total number of monthly hemodialysis treatments between MA and MI patients after implementing CPS. Another regression model, regressing on the changes in the monthly claims of dialysis treatments, showed a significant negative coefficients for the MA (beta= -70725, p<0.05). CONCLUSION: The result of significant decrease in total charges for hemodialysis treatments among MA patients as compared to MI patients suggest that there was cost reduction in MA program after the CPS.