Background: Spontaneous bacterial peritonitis (SBP) is a unique and a widespread complication in cirrhotic patients. The prevalence ranges from 10 to 30% in cirrhotic ascitic patients. Aim of work: to evaluate role of Homocysteine level in ascetic fluid in diagnosis of ascetic fluid infection. Methods: Patients were classified into two groups: Group I includes 45 patients with cirrhotic ascites complicated with SBP and group II includes 45 patients with cirrhotic ascites and without SBP. all patients were subjected to full history taking, complete clinical examination, and laboratory investigations and Measurement of hemocycsteine level in ascetic fluid sample. Results and conclusion: There was no statistically significant difference found between the two studied groups regarding glucose ,total protein in ascetic fluid of the studied cases while there was statistically significant difference found between them regarding albumin in ascetic fluid with highly significant difference between them regarding tlc and neutrophils in ascetic fluid ( increase in sbp group in comparison to non sbp group), There was highly statistically significant difference found between the two studied groups regarding homocysteine in ascetic fluid of the studied cases, The cut-off level of baseline homocysteine measurement that was considered to have predictive value for detection of SBP was 4.9, with a sensitivity of 91.11%, specificity of 93.33%, +ve predictive value of 93.2% and -ve predictive value of 91.3%, denoting that homocysteine measurement is considered as good test for prediction of spontaneous bacterial peritonitis.