patients with idiopathic pleural effusion were observed under fiberoptic bronchoscopy and the levels of adenosine deaminase, carciembryonic antigen were measured in pleural effusion. 29 out of 62 patients with idiopathic pleural effusion observed under fiberoptic bronchoscopy were identified to be ling cancer. The level of adenosine deaminase in pleural fluid were higher in the group of patients with tuberculous pleuritis than that with lung cancer (p<0.01). The level of carciembryonic antigen in pleural fl...