The author deals with the diagnosis and differential diagnosis of pleural effusions. The differential diagnosis depends
on thoracentesis. The pleural effusion should by examined biochemically, cytological, bacteriologically and the results
should be completed by histologically. Before thoracentesis, it is important to obtain and analyze the personal history,
perform a physical examination, including a biochemical analysis, bacteriological tests, x-ray and/or CT examination
and an ultrasonography of the chest and abdomen. The pleural fluid differential diagnosis should result in the suitable
management of the pleural effusion.