To define the effectiveness of C-reactive protein (CRP) as indicator for early detection of the post-operative infection, it is essential to exclude possible normal changes of CRP influenced by surgery itself. We analyzed 44 patients who had done orthopaedic surgeries without any evidence of infection preoperative and postoperatively from May to Aug. 1995 at Dongsan medical center, Keimyung University. We checked the levels of Erythrocyte sedimentation rate (ESR) and CRP levels at preoperative and postoperative 1, 3, 5, 7, 9, 11, 13, 15, 17, 19 and 21st day in all cases. In all cases, ESR increased up to 60mm/hr maximally and CRP increased to more than 10mg/dl at least one occasion within the first 3 weeks postoperatively. However CRP showed more rapid changes than ESR. The mean value of the CRP was increased maximally (7.2mg/dl) at 3 day after operation and then decreased rapid until 11 day. ESR was also increased at 3 day after operation, but it sustained high level until 21 day after operation. CRP appears to be more sensitive and rapid indicator as an acute phase reactant for the operation itself because CRP revealed more earlier and accentuated change after the operation. The changes of CRP showed same pattern regardless of operation time, use of tourniquet, use of transfusion and gender. In conclusion, within 3 day after operation, the high titer of CRP can not to be an indicator for early detection of the infection, because normal high titer can be developed by surgery itself. If there notes persistent high titer or more increasing pattern of CRP after postoperative 3 day or abnormal high titer of CRP after 11 day postoperatively, infection may be highly suspicious.