Introduction: Tuberculosis is the principal cause of pleural exudates in countries with a high prevalence of this disease. Therefore evaluation of new fast and low cost diagnostics tools seems a good strategy in order to allow a specific treatment. Objective: To show and prove the utility of the determination of Adenosine Deaminase levels (ADA) and its isoenzymes ADA1 and ADA2 in the pleural fluid, in the diagnostic of Pleural Tuberculosis. Methods: a descriptive and prospective study of a sample of selected cases admitted in the Pulmonology Service of Hospital Dr. José Ignacio Baldó. The determination of the Adenosine Deaminase levels was done through the Giusti Method. Descriptive statistics were used, also, student t, chi squared; and the sensibility, specificity and predictive values were calculated as well. Results: 41 patients were included, 51% were females with ages between 19 and 71 years old (X: 45 +/- 19.4). The etiology observed with a higher frequency was tuberculosis (51,2%) followed by the Metastatic Neoplasm, the sensibility, specificity, BPP, VPN and accuracy in the levels of ADA > 40 UI/L for the diagnostic of Pleural Tuberculosis were: 85.7, 85.0, 85.7, 85.0 y 85.4% respectively and for the relation ADA1/ADA2 < 0.45: 95.2, 30.0, 58.8, 85.7 y 63.4%. Conclusions: In this research, the determination of the levels of the isoenzymes activities ADA1 and ADA2 didn’t provide a diagnostic advantage about the determination in the activity of the total ADA in the Pleural Tuberculosis. The activity levels of the ADA could be used as an initial test to guide other diagnostic and therapeutic procedures in pleural exudates.