The present study was under taken to evaluate the diagnostic value of interferon gamma in the sera or exudative effusion (pleural or ascitis) of tuberculous Egyptian pediatric patients, suffering from pulmonary tuberculosis or extra pulmonary tuberculosis. We evaluated 50 patients aged less than 15 years with tuberculosis, 25 patients also in the same age range and living under the same socio-economic conditions suffering from non tuberculous exudative pleural or ascitic effusions were considered as controls. Interferon gamma was measured by immunoassay in the tuberculous group in 38 exudative pleural effusions, 7 exudative ascitic effusions, and in 10 sera of tuberculous patients, culture technique was done trying to detect interferon gamma in small amounts present in 10 pleural and ascitic exudative effusions. Results were compared to levels of interferon gamma found in patients in the control group in 15 exudative pleural effusions with non tuberculous etiology (12 suffering from bacterial pneumonia, 3 suffering from bacterial infection on top of malignancy. 5 ascitic exudative effusions (2 patients had malignant ascitis, 2 patients were suffering from chronic renal failure) and 1 patient had septic peritonitis, 5 sera of healthy subjects. Culture technique was performed in 5 pleural and ascitic effusions in control patients suffering from small amounts of effusion. At a cut off point 10.8 pg/ml sensitivity was 96% and specificity 100% so it is obvious that IFN can be used to differentiate tuberculous exudative pleural effusion and ascitic from non tubercuolus etiology.