To determine the diagnostic features of tuberculous peritonitis that distinguish it from other causes of ascites, 50 ascitic patients were examined prospectively. The biochemical, bacteriological and immunological properties of ascitic fluid from 11 patients with tuberculosis, 24 patients with hepatic cirrhosis and 15 patients with malignant ascites were compared. High values of adenosine deaminase activity (ADA) and gamma interferon ( IFN - g) were detected in ascitic fluid of tuberculous patients. The sensitivity, tests of IFN - g ADA and PCR in the diagnosis of tuberculous ascites were 90.9%, 81.8%, and 36.3%, respectively while the specificity tests of all were 100%. A significant positive correlation was present between ADA activity and IFN - g level in ascitic fluid. The same correlation was detected between ADA activity and total protein concentration. However IFN - g was considered superior to ADA in diagnosis of tuberculous peritonitis in cases with decreased ascitic fluid total protein. Laparoscopic peritoneal biopsies in the seven tuberculous patients, revealed histopathologic granuloma and gave positive culture for T.B. It is concluded that, increased ascitic IFN - g and ADA are useful, rapid non invasive screening tests in diagnosis of tuberculous peritonitis, whereas PCR has a limited utility. The best confirmation is by laparoscopic peritoneal biopsy followed by histopathologic and culture studies.