Background Although treatment of DIC is said to be more effective when it is started at early stage, early diagnosis of DIC occurring in surgical infectious SIRS (Septic DIC) is difficult because in these cases decrease in blood fibrinogen levels rarely occurs and the magnitude of elevation of blood FDP is usually small. In the present study, we had observed the changes in blood fibrinogen production in the liver and also we investigated the correlation between the blood levels of other acute phase reactant and IL-6. Patients and method Blood was withdrawn from 18 septic DIC cases and 20 non-DIC infectious SIRS cases at 4 points (the day of DIC diagnosis, next day, the 3rd day and the 5th day). The blood samples are analyzed for IL-6, C-reactive protein (CRP) fibrinogen, Thrombin antithrombin III complex (TAT), α2-Plasmin inhibitor-plasmin complex (PIC) and D-Dimer. Results 1. There was a significant correlation between CRP and IL-6 (r = 0.73, P < 0.0001) in septic DIC cases. 2. Although fibrinogen did not significantly correlate with IL-6 (r = 0.027, P < 0.84), there was a significant correlation between CRP and fibrinogen (r = 0.55, P < 0.0001) in septic DIC cases. 3. We could also observe a significant correlation between CRP and fibrinogen (r = 0.78, P < 0.0001) in non-DIC infectious SIRS cases. 4. A scattered graph was made between CRP and fibrinogen in septic DIC cases and non-DIC infectious SIRS cases (Fig. 1). While blood fibrinogen in the half of septic DIC cases, its values were lower than those in non-DIC infectious SIRS cases when patient of both group had same CRP. Discussion From these data, we can predict fibrinogen level in correspondence with blood CRP in individual SIRS cases. When measured fibrinogen was lower than this level, we could identify the pathophysiological state in which fibrinogen was consumed (hypercoagulation). And this would lead to early diagnosis and evaluation of severity of the septic DIC.