Serial non-invasive studies including echocardiography were performed for the evaluation and follow-up of the cardiac lesions in six cases with genetic mucopolysaccharidoses. These cases were classified by the enzyme assay into one case of Scheie syndrome, three of Hunter syndrome, one of Sanfilippo syndrome and one of Maroteaux-Lamy syndrome. The echocardiographic examination revealed the most striking change in the mitral valve, which was progressive with increase of the age in most cases. The mitral valve echo was dense and multilayered with a decreased diastolic descent rate (DDR) in the M-mode echocardiogram, and its thick leaflets showed diminished opening on the two-dimensional echocardiogram. The aortic valve echo was also dense in three cases inducing one case with the prolapse of the non-coronary cusp into the left ventricular (LV) cavity. The pulmonary and tricuspid valves showed an unremarkable change, although the echocardiographic signs of pulmonary hypertension was observed in two cases. Diffuse hypertrophy of the interventricular septum and LV posterior wall was observed in five cases and apical hypertrophy was found in a case of Hunter syndrome (Case 2). Parameters of the LV contractility showed almost normal values but the distensibility of the LV posterior wall was impaired in two cases, suggesting stiffness of the cardiac muscle. Although no ischemic change was observed on the electrocardiogram, the echo density of coronary artery wall was not uniform on the two-dimensional echocardiogram and dilated coronary artery was found in two cases. Phonocardiograms disclosed an aortic regurgitant murmur in one case and an apical mitral regurgitant murmur in two cases. In one case of Scheie syndrome, a pansystolic murmur (Levine 3/6) and a mid-diastolic rumble (Levine 2/6) were present at the age of 15 and 16, but after the transient increase in the loudness these disappeared at the age of 18 and only an ejection systolic murmur is audible at the present time, while the mitral valve showed a progressive limitation of the movement on the two-dimensional echocardiogram. Contrary to the reduced DDR and diminished opening of the mitral valve in 3 cases, neither diastolic rumble nor opening snap was recognized in the phonocardiogram. The echocardiographic findings seemed to reflect the patho-anatomical manifestation of this disease, and thus, the periodical echocardiographic evaluation is rewarding to assess the cardiac lesions and their progression in mucopolysaccharidoses.