Pleural effusions can be catagorised in to transudative effusions or exudative effusions. Causes include cardiovascular disease, infection and neoplasm. Diagnosis is the key to determining what management is required. History and examination can elicit the cause of the effusion and radiological investigations can be a useful adjunct. Thoracocentesis and laboratory testing of the pleural fluid is usually diagnostic and can direct further investigations or treatment. Management of the pleural effusion ultimately varies according to the diagnosis but can be either directed towards reversing the cause of the effusion or treating the symptoms that arise as a result of the effusion.