The objective of this study was the prospective evaluation of the IgG antibody levels to mycobacterial antigen 60 (A60) in serum and pleural fluid and their role in the diagnosis of tuberculous pleuritis. The level of IgG was measured by Elisa in 30 patients with tuberculous pleuritis and 48 control subjects with pleural effusion (24 with carcinoma, 10 with transudative pleural effusion, 11 with empyema or parapneumonic effusion, 1 with pulmonary embolism and 2 due to systemic lupus erythematosus). The median titers of IgG against A60 of both serum and pleural fluid from tuberculous patients [445.6 +/- 133.56 and 263 +/- 72.58 Elisa units (EU) respectively] were significantly higher than those of corresponding median values (97.3 +/- 8.35 and 41.3 +/- 4.93 EU) of the control group (p < 0.01 and p < 0.01, respectively). Considering 240 units as cutoff point for a positive test in serum, the sensitivity was 53.3% and the specificity 100%. In the pleural fluid the cutoff point value was established at 150 units, with a sensitivity of 50% and specificity of 100%. We concluded that Elisa using A60 is a reliable and rapid test with an acceptable sensitivity and magnificent specificity.