Prospectively, clinical and biochemical data of 83 patients with a diagnosis of pericardial effusion were studied. The etiologies were as follows: Idiopathic: 42 cases (50%); Tuberculous: 18 cases (22%); Neoplastic: 14 cases (17%); Other: 9 cases (11%) with a miscellaneous etiology. Sedimentation rate resulted significantly higher in Tuberculous group (67-102), p<0.05. The highest values of adenosine deaminase in pericardial fluid were observed in Tuberculous group (110 U/l), p<0.001. Diagnosis of tuberculosis was established by culture of the bacillus in sputum in 8 cases and by pericardial biopsy in 11 patients. Analysis of the pericardial fluid leads to diagnosis in 25 cases (30%). The pericardial biopsy resulted as the most reliable method for the diagnosis of tuberculous pericarditis.