Myxoma is the most common type of primary cardiac tumor and about 75% of myxomas occur in the left atrium of the heart. Most myxomas are diagnosed by echocardiography. The growth rate of myxoma is clearly unknown and newly developed myxoma is difficult to understand clearly the onset of growth. We describe the case of a newly developed huge left atrial myxoma($7{ imes}7cm$)which showed no echocardiographic evidence of the tumor four years ago. Four years later the patient underwent transthoracic echocardiography due to preoperative evaluation that was normal. Nine months later, she presented with dyspnea. Transthoracic echocardiography showed a large mass located in left atrium. Pathology showed a myxoma that measured $7{ imes}7cm$ implying a growth rate of $0.15{ imes}0.15cm/month$.