It has been shown that CD11b molecules on monocytes is associated with migration and HLA-DR molecules on monocyte have function to present antigens against T cell, resulting in activation of cellular immunity. We have analyzed that phenotypic change of monocytes and alteration of plasma cytokine levels (IL-6, IL-8, IFN-gamma) due to surgical stress. Materials and method Gastrectomy (n=23, G group) , esophagectomy (n=8, E group) , pancreaticoduodenectomy (n=7, P group), Emergency operation against acute abdomen (n=4, Em group) were performed. The levels of CD11b and HLA-DR expression on peripheral monocytes were assayd by flow cytometric analysis (FACScan) and plasma IL-6, IL-8, IFN-gamma were measured by ELISA on preoperative period, 1st POD,3rd POD,5th POD,7th POD,and 7th POD,respectively. Every groups had no major postoperative complication. Results There is no significant difference of monocyte counts among groups. The mean fluorescence intensity (MFI) of CD11b expression were 37.7,29.6,32.1,12.3(G,E,P,Em group) on preoperative period, 29.8,18.6,29.4,19.1, on 1st POD and 33.0,18.3,22.5,39.7, on 14 POD,respectively. The MFI of HLA-DR were 62.7,61.9,48.7,113.5(G,E,P,Em group) on preoperative period, 46.9,65.0,38.8,27.0, on 1st POD and 48.0,83.9,27.5,98.2, on 14 POD,respectively. The plasma IL-6 levels were markedly increased preoperatively compared to the other groups and recovered to normal levels postoperatively. The plasma IL-8 levels of E groups were increased preoperatively and postoperatively compared to G or P group. Conclusion The decreased expression of CD11b and hypercytokinemia such as IL-8 in E group might be related to the mechanism of SIRS.