The causes and situation of exudative pleural effusion vary from one area to another. A cross-sectional study was conducted on 327 patients with exudative pleural effusion in South Khorasan province (Iran). The patients were older than 12 years and comprised 172 (52.6%) males and 155 (47.4%) females. The study commenced in 2007 with seven years duration. The Light’s criteria were used to define...