Pleural effusion (PE) is a very uncommon manifestation of sarcoidosis. It is equally observed in men and women, can appear at any age and in all radiologic stages, though it is more common in stages i and ii. Effusions have usually a mild or medium size and mainly involve the right side. Various mechanisms can be implicated. PE will be a serous exudate if there is an increase in the capillary permeability due to direct involvement of the pleural membrane, a chylothorax if mediastinum lymph nodes compress the thoracic duct and/or the lymphatic drainage from the pleural cavity, an hemothorax if granuloma compress or invade pleural small vessels or capillaries, and even a transudate if there is compression of the inferior vena cava, atelectasis due to complete bronchial obstruction or when the resolution of the PE is incomplete with chronic thickening of visceral pleura (trapped lung). It manifests biochemically as a pauci-cellular exudate with a predominance of lymphocytes, though there can be a preponderance of eosinophils or neutrophils. Protein concentrations are usually proportionately higher than lactate dehidrogenase, adenosine deaminase is normally low and it is possible to find increased levels of CA-125 in women. The tuberculin test is negative and pleural or lung biopsies yield the diagnosis by confirming the presence of non-caseating granulomata. These PE can have a favorable self-limited outcome, even though in most cases treatment with corticosteroids is needed, while surgery is required in a few cases.