Ascites can present a challenging diagnostic problem. Bacteria caus- ing spontaneous bacterial peritonitis (SBP) may difer in patients with and without underlying malignancies. To date, reports focusing on patients with malignancies and ascites are less. The aim of the present study was to determine the prevalence and causative agents of SBP in cancer and non cancer patients and the antibacte- rial susceptibilities of these microorganisms. Also, to identify diferences, if any, in polymorphonuclear (PMN) cell count, interleukin (IL)-6 concentration, and diferent biochemical diagnostic parameters, we analyzed for infected and non infected as- cites in both groups.