Ovarin hyperstimulation syndrome (OHSS), an iatrogenic complication of ovarian stimulation, shows varying degrees of clinical manifestations. The pathogenesis of OHSS is an increase of vascular permeability resulting in hypovolemia, thromboembolism, ARDS, and death in sometimes. Pleural effusion is also a result of an increase of vascular permedability in the pleura. Thoracentesis is sometimes required to relieve dyspnea. We report a case of OHSS with bilateral exudative pleural effusfion is a 23 year-old female with resting dyspnea. She was received clomi;hen, FSH, and LH for the treatment of irregular menstruation twenty days previously. The ultrasonogram showed severe ascites and bilaterally huge ovary, and chest radiography showed bilateral effusion. Therapeutic thoracentesis and paracentesis were done for relief of the dyspnea. Two weeks later the bilateral effusion and symptoms disappeared spontaneously.