Of a total sixtytwo patients covering all the spectrum of genetic ASH, who were studied by heart catheterization, M-mode echocardiography and phonomechano cardiography, five patients (four with the obstructive variety of the disease) showed clinical evidence of chronic congestive heart failure with ankle edema and hepatomegaly (group I). Their data were compared with those of fifteen "obstructed" patients who were not in heart decompensation (group II). No statistically significant differences were found between groups I and II in terms of L.V. internal transverse dimensions and in terms of L.V. systolic function. Conversely a statistically significant difference was found between the two groups in terms of left atrial and right ventricular dimensions (P less than 0,001), which were markedly increased in groups I. These findings strongly suggest that in patients with ASH and congestive heart failure there is a reduction in L.V. compliance (or distensibility), whereas L.V. systolic function is essentially preserved. The persistence of severe L.V. outflow obstruction in four patients of I group gives further confirmation to these observations. The use of beta-blockers (in association or not with cardiac glycosides) seems therefore to preserve its validity in the treatment of patients with ASH and heart failure, particulary when severe L.V. outflow obstruction is present. Cardiac glycosides are indicated in the forms with little or no obstruction to L.V. ejection.