Pleurisy is a common syndrome revealing or complicating numerous diseases. It is suspected on dyspnea or chest pain, with or without dullness to percussion. Diagnosis is confirmed almost always by chest roentgenogram but CT scan and echography can help in case of small pleural effusion. Etiologic research is based on pleural fluid analysis. The dosages of protein and LDH separate transudate from exsudate. Cellular differential count and bacterial and mycobacterial culture must systematically be performed. Other pleural analysis are discussed when specific illness are suspected. In case of exsudative pleural effusion, histological examination of pleural tissue sample is often necessary. Despite the etiological search, some pleurisy remains without specific diagnosis and necessitate a prolonged follow up with sometimes repeated thoracocentesis or biopsy. Treatment of pleurisy is based on the treatment of the underlying disease and the evacuation of pleural fluid.