BACKGROUND: Little information is available concerning the value of bronchoscopy in patients with a lymphocytic exudative pleural effusion in which percutaneous pleural biopsy have been regarded as cornerstone in investigating the etiology. Recenfly, a few reports suggest that bronchoscopy may be more effective diagnostic method in patients with unexplained pleural effusion accompanied by hemoptysis or other roentgenographic abnormalities, such as mass, infiltrate, atelectasis. METHOD: After initial examinations of sputum and pleural fluid through thoracentesis in 112 patients(male 75 cases, female 37 cases, mean age 53.2 years) who were admitted for evaluation of the cause of pleural effusion, we performed bronchoscopy and closed pleural biopsy in most patients with undiagnosed lymphocytic exudate and compared the diagnostic yield of both invasive methods according to hemoptysis or other roentgenographic abnormalities, and investigated the sole diagnostic contribution of bronchoscopy. RESULTS: Tuberculosis(57 cases, 51%) was the most common cause of pleural effusion Percutaneous pleural biopsy showed more diagnostic yield than bronchoscopy regardless of presence or absence of other clinical or radiologic abnormalities. In 25 cases with unknown etiology after pleural biopsy, additional diagnostic yield by bronchoscopy was 36% (4/11) in patients with associated features and only 7% (1/14) with lone effusion, and, as the sole mean for diagnsosis in all patients with pleural effusion, was only 4.5% (5/12) Condusion: In a region of high prevalence of tuberculosis as a cause of pleural effusion, percutaneous pleural biospy is more effective method when invasive method is required for confirmative diagnosis of unexplained lymphocytic exudative pleural effusion, and bronchoscopy is unlikely to aid in the diagnosis of lone pleural effusion.