Even though hypothyroidism accompanies pericardial effusion, most patients have no symtom, and so its effusion is dignosed accidently. The pericardial effusion may be found in as many as 30% of adults patients, but pericardial effusion as the presenting feature of hypothyroidism is rare cause of dyspnea. We experienced two cases of hypothyroidism presenting with dyspnea in 46 year-old female and 36 year-old female patients. Their pericardial effusion was detected by echocardigraphy, and it resolved simultaneously with subsided dyspnea after 2 or 3 month therapy of thyroxine. (J Kor Soc Endocrinol 7: 295~299, 1992)