In an attempt to differentiate between three important but clinically similar conditions of exudative ascites like tuberculous peritonitis, spontaneous bacterial peritonitis (SBP) and malignant ascites, we evaluated the biochemical parameters of ascitic fluid as a diagnostic aid. The serum ascitic albumin gradient (SAAG), lactate dehydrogenase (LDH), pH, adenosine deaminase (ADA), carcino-embryonic antigen (CEA) ,carbohydrate antigen (CA-125) and gamma Interferon levels were measured in 34 patients with tuberculous peritonitis, 24 patients with SBP and 22 patients with ascites due to malignant disorders. The LDH level was significantly lower in tuberculous peritonitis patients than in malignant and SBP groups. A value of < 110 U/l gave the assay a sensitivity of 94% and a specificity of 93 %, positive predictive value of 89 % and negative predictive value of 96% for tuberculous peritonitis. The ADA activity was significantly higher in tuberculous peritonitis group than in the other two groups. A cut off value > 33 U/l gave the ADA test a sensitivity of 88 %, specificity of 100 %, positive predictive value of, 100 % and a negative predictive value of 94 % for tuberculosis. A pH value of <7.26 with high SAAG (> 1.1 g/dl) predicted SBP with reasonable accuracy. Elevated ascitic fluid CEA ( > 2 ng/ml) and CA -125 (> 35 U/l) was found exclusively in cases of malignant ascites. Gamma Interferon level was higher in tuberculous peritonitis than in other cause of exudative ascites and cut off =>3.2u/ml gave the assay a sensitivity of 93% and specificity of 98%,positive predictive value and negative predictive value of 96%. All these tests are rapid, non-invasive, and easily reproducible and offer good predictive accuracy which is comparable to that of more invasive procedures like peritoneoscopy and biopsy