We have investigated the use of polymerase chain reaction (PCR) for the rapid diagnosis of pleural tuberculosis. The study was composed of 21 patients with pleural tuberculosis, confirmed by culture or pleural biopsy, and 86 control subjects. The PCR assay was based on detecting a 123-bp DNA segment belonging to the insertion sequence IS6110, specific of Mycobacterium tuberculosis complex. In 21 patients diagnosed with pleural tuberculosis, Ziehl-Neelsen staining was positive in three (14%) (95% CI, 7 to 21%) and pleural fluid culture in 11 (52%) (95% CI, 43 to 61%). Pleural biopsy revealed granulomas with caseous necrosis in 72%, and the culture was positive in 67% of the patients. Adenosine deaminase activity determination was positive (> 45 IU/L) in 86% (95% CI, 79 to 93%). The sensitivity and specificity for PCR was 81% (95% CI, 74 to 88%) and 100% (95% CI, 95 to 100%), respectively. All culture-positive specimens were PCR positive. We conclude that PCR is a rapid, sensitive, and specific method for the diagnosis of pleural tuberculosis. However, further prospective studies are required to properly evaluate the yield of the technique.