Background: Patients with liver cirrhosis (LC) are at high risk for developing bacterial infections. Serum Procalcitonin (PCT) level increases during bacterial infections but usually remains low during viral infections and nonspecific inflammatory diseases. Objective: evaluate the diagnostic role of procalcitonin in discrimination between SBP and culture negative neutrocytic ascites. Methods: This study was done on fifty four (54) patients with liver cirrhosis, Twenty seven (27) (Group I) of them suffering from classic SBP on top of cirrhosis and the other twenty seven (27) (Group II) suffering from liver cirrhosis with culture negative neutrocytic ascites. They were chosen from those who admitted to Hepatology and Gastroenterology Department, Banha University. Results: There was statistically significant difference between Procalcitonin as regard discrimination group I from group II. The mean Procalcitonin in group I was 1.63 (±0.68) SD with range (0.30 – 2.50). The mean Procalcitonin in group II was 0.58 (±0.45 SD) with range (0.02 – 1.80). Using roc curve for procalcitonin to discriminate group I from group II it showed high significance above 0.8 with area under curve of 0.894, sensitivity 85.19, specificity 70.37, positive predictive value 74.2 and negative predictive value 82.6. According to relation between procalcitonin and different parameters in group II, there was statistically significant difference between procalcitonin as regard encephalopathy, in group II. Conclusion: PCT level was higher in liver cirrhosis patients with SBP than CNNA which indicated it may represent as a simple biomarker for differentiating SBP from CNNA.