Background and study aim: Cirrhotic patients with ascites show a higher susceptibility to bacterial infections, monocyte chemotactic protein-1 (MCP-1) secretion is up-regulated during chronic hepatitis and correlates with the severity of hepatic inflammation. The aim of this work is to determine the level of expression of MCP-1 gene in blood and ascitic fluid in cirrhotic patients with and without spontaneous bacterial peritonitis (SBP) to evaluate its role in pathogenesis of SBP and its role in diagnosis. Patients and Methods: This study included 15 healthy subjects served as control group in addition to 35 cirrhotic patients due to HCV infection with ascites; classified into two groups, cirrhosis without SBP (15 patients) and cirrhosis with SBP (20 patients). All groups were subjected to quantitative estimation of MCP-1 gene expression in blood by real time PCR. In SBP and non SBP groups the gene expression were assessed in ascitic fluid also at diagnosis and reassessed in SBP group after treatment. Results: Blood and ascitic fluid expression of MCP-1 gene were significant higher in SBP group than non SBP group and control group. SBP group showed a significant decrease in level of MCP-1 gene expression in blood and ascitic fluid after resolution of infection by appropriate treatment of SBP. Conclusion: MCP-1 gene expression in both blood and ascitic fluid may be related to pathophysiology and course of SBP and can be used as a marker for diagnosis.