We report 2cases of calcified amorphous tumor（CAT）in hemodialysis patients. Case 1is a68-year-old man who had received hemodialysis for 11 years due to diabetic nephropathy withrenal failure. He was admitted because of shortness of breath. After appropriate diagnostictesting,we found a 7mm movable tumor on the side of the left atrium causing stenosis at the baseof the left anterior descending artery（LAD). We suspected this to be a myxoma. We performeda myxomectomy and coronary artery bypass grafting（CABG). The tumor had a stalk andhemogenesis on the surface. Case2is a 63-year-old man who had received continuous ambulatoryperitoneal hemodialysis for 18months due to diabetic nephropathy with renal failure. He wasadmitted because of subjective complaints of chest compression and shortness of breath.Ultrasound cardiography revealed 16mm tumor on the posterior mitral valve leaflet with mildmitral regurgitation. We removed the tumor and placed a mitral valve prosthesis. Grossly thetumor was encapsulated with endocardium.On pathological examination, both tumors were CATs. CAT is a lesion characterized bycalcified fibrin deposits. Preoperative diagnosis of these tumors is difficult. While manysurgeons elect to conservatively watch these tumors among dialysis patients, when they aremovable, there is a risk of embolism and we should remove the tumor early.