Rupture of the aortic valve falls into two distinct clinical patterns; the first is rupture of the normal valve after some unusual stress or strain, particularly that of heavy lifting; the other occurs when the valve is disorganized by bacterial endocarditis and erosion leads to rupture. We wish to present an example of the second kind and emphasize a physical sign that may be helpful in detecting the aortic rupture clinically; namely, a sudden fall or complete disappearance of the diastolic blood pressure. Clinical signs of established aortic insufficiency are well known, but the observation of a normal diastolic pressure that declines significantly or disappears entirely has not been emphasized. REPORT OF A CASE L. C., a 44-year-old man, was admitted to the medical service of the University Hospitals because of chest pain and fever. Four weeks before admission he had a toothache and a swollen upper lip. Before he