Reflected ultrasound has been used for investigation of the mitral valve region in early infancy. The material consists of two patients with mitral atresia, three patients with mitral stenosis and aortic valvular atresia, five patients with mitral and aortic valvular stenosis, one patient with cor triatriatum, and one patient with severe degree of aortic valvular stenosis with a normal mitral valve. The results are compared with ultrasoundcardiographic findings in ten infants without heart disease. A specific abnormal echo was obtained in cases with mitral atresia and cor triatriatum. The patients with a combination of mitral and aortic valvular lesions could be separated into two groups by means of ultrasoundcardiography. This separation reflected the functional state of the left ventricle based on the degree of mitral stenosis and hypoplasia of the left ventricle.This noninvasive technic has been found useful as a complementary method for the investigation of the mitral valve region. It can even be performed in seriously ill infants.