DPC（ Diagnosis Procedure Combination） was introduced in our hospital in June 2006, and we anticipated that its introduction would be followed by a reduction in medical treatment fees for patients hospitalized for pneumonia. Here, we report a study of the changes in inpatient medical treatment fees for pneumococcal pneumonia before and after the introduction of DPC. We created 156 types of electronic clinical pathways (e-CP), and compared the difference between medical treatment fees under DPC and under itemized calculation. Our subjects were 349 patients who were hospitalized from October 2004 to March 2010. We divided them into three groups, Group A: patients during the itemized-payment period, Group B: patients during the pre-revision period, and Group C: patients during the post-revision period. Moreover, each group was classified by the degree of penicillin resistance of the Streptococcus pneumoniae. The medical treatment fees of each group were examined. Simulations using the e-CP showed a decrease in medical treatment fees in groups of patients for whom DPC had been introduced, while the post-revision group showed a further reduction in medical treatment fees. However, medical treatment fees for actual inpatients in Groups B and C under DPC were higher than under itemized calculation. On the other hand, we expected an increase in medical treatment fees due to penicillin resistance in S. pneumoniae, but saw no such change. The increase in medical treatment fees after the introduction of DPC seems to be primarily due to the addition of secondary illness names that changed pneumonia to a more expensive illness under DPC, and the cost of antibiotics actually decreased.