This patient had an attack of subacute bacterial endocarditis involving the aortic valve. He developed fulminating congestive heart failure secondary to acute aortic regurgitation, terminating in the prosthetic replacement of his aortic valve. The echo from the aortic valve demonstrated marked coarse fluttering of the cusps, both in systole and in diastole. The two cusps did not coapt in diastole. The echo from the mitral valve showed features of acute regurgitation. The carotid pulse tracing showed marked slurring in its descending limb. The postoperative echocardiogram showed absence of these findings. We suggest that a diagnosis of flail aortic valve be considered in patients suffering from significant isolated aortic regurgitation in the absence of calcification of the aortic valve and with a negative VDRL test for syphilis.