Background: In cirrhosis, spontaneous bacterial peritonitis )SBP) is the most frequent infection . Rapid and precise identification of bacteria in clinical and scientific settings has been greatly aided by the 16S rRNA gene. Objective: Assessment of role of 16S rRNA gene in diagnosing SBP among cirrhotic ascitic cases. Patients and methods: our study was done on 60 adults cirrhotic ascitic patients, classified to 2 groups: Group I (SBP group ═ 38): involved all cases with ascitic fluid PMNL ≥ 250 cells/mm3, Group II (Non SBP group ═ 22): involved all cases with ascitic fluid PMNL < 250 cells/mm3. Ascitic fluid (AF) examination, bacterial culture and polymerase chain reaction (PCR) for detection of DNA were assessed among all cases. Results: Significantly greater levels of CRP were seen in the SBP group in comparison to the non-SBP group. Culture had sensitivity 53.3%, specificity 68.2%, PPV 70.5%, NPV 64.9 % and accuracy 60% for SBP diagnosis. PCR had sensitivity 94.7%, specificity 63.3%, PPV 81.8%, NPV 87.5% and accuracy 83.33% for SBP diagnosis Conclusion: Rapid and precise identification of AF infection is crucial for successful therapy, and polymerase chain reaction (PCR) detection of the 16s rRNA gene in ascitic fluid demonstrates this.