The aim of this study is to clarify the relationship between CRP and postoperative infection after cardiovascular surgery. We had 5 cases of surgical site infection, and 3 cases of infective endocarditis (IE) among 57 patients selected for this study out of 405 patients who had undergone cardiovascular surgery from May 1995 to March 2005. CRP, WBC and body temperature (BT) were evaluated during 1 week after the operation. Our results showed not only that the mean value of CRP level in the 49 non-infection patients attained the peak on the 2nd or 3rd day after the operation (18.2 +/- 4.7 and 17.7 +/- 5.7 mg/dl), but also that each patient in this group showed the same pattern of CRP sequence. CRP in the 5 cases of postoperative infection showed different patterns from that in the non-infection group. CRP in 3 cases of valve replacement for IE showed significantly higher level than that in 16 cases of valve replacement without IE through 1 week after the surgery. WBC level in the non-infection group reached the peak just after the operation (11.3 +/- 4.4 x 10(3)/microl) and then decreased gradually during 1 week after the operation. WBC in the 3 cases of valve replacement for IE, did not show different sequence pattern from that in the 16 cases of valve replacement without IE. WBC in a case of postoperative mediastinal infection showed a similar pattern of sequence to that in the non-infection group although it showed a remarkably high level of CRP sequence through 1 week after the surgery. BT in the non-infection group became the lowest just after the operation and reached the peak 8 hours after the operation. It then decreased gradually during 1 week after the operation. Our study demonstrates that CRP sequence after the surgery might be useful to detect postoperative infection after cardiovascular surgery.