A 50-year old man was evaluated for pleuritic pain.. Chest roentgenogram showed diffuse parenchymal infiltrates and bilateral effusion that, on thoracocentesis, was found to be a bloody fluid. Biopsy of paratracheal nodes demonstrated abundant noncaseating granulomas consistent with sarcoidosis. Prednisone therapy resulted in rapid disappearance of the pleural effusion, progressive clearing of parenchymal infiltrates, and marked improvement of pulmonary function tests. Sarcoidosis should be included in the differential diagnosis of bloody pleural effusion.