Lambl's excrescences are the fibrous structures which are attached to the heart valve, and usually the presence of Lambl's excrescences alone is not an indication of operation. The operative indications of isolated Lambl's excrescence is still controversial, because some reports indicated cross relationship between Lambl's excrescences and cerebral embolism. Based on these facts, we discussed our 3 cases of Lambl's excrescences. Two of the cases had been complicated with severe mitral regurgitation and Lambl's excrescences were resected at the time of mitral valve plasty. In another case, Lambl's excrescence was found with echocardiography during chronic heart failure therapy. This patient had a past history of cerebral infarction, but no relationship of cerebral infarction was suggested. In this case, cardiac surgery was not required, so we followed isolated Lambl's excrescence without resection in this case. One operated case, which had infective endocarditis was suspected by echocardiography, had slighted inflammatory reaction but blood culture was negative. Diagnosis of Lambl's excrescence was made by histopathological examination. One report suggested that the cause of the cerebral infarction is not Lambl's excrescence itself but the thrombi around Lambl's excrescence. However, we hesitate to operate on isolated Lambl's excrescence. Based on some reports, it is useful to resect Lambl's excrescence when a concurrent cardiac operation is carried out to avoid cerebral embolic events.