ALTHOUGHit has been a century and a quarter since the first published account by Hope in 1839 1,2 of a ruptured congenital aneurysm of the sinus of Valsalva, there have been fewer than 100 cases of congenital aortic sinus aneurysms reported in the medical literature.3 Except for the work of Edwards et al,4,5 detailed description of the histopathology of the lesion is lacking. The incidence of acquired aortic sinus aneurysms is more difficult to determine from the literature, but the general impression gained is that the acquired type is even more rare. Recently, we have had the opportunity of seeing two patients, admitted within 14 days of each other, in whom the diagnosis of aortic sinus aneurysm was later confirmed by autopsy. Both because of the rarity of this condition and the paucity of detailed histologic studies, these cases are being presented. masses or tenderness ; bowel sounds were normal. Rectal examination showed no abnormalities. There was no peripheral edema, clubbing, or cyanosis, and there were no splinter hemorrhages. The femoral pulses were forceful, but there was no bruit. Neuro¬ logical examination was unrevealing. The clinical impression was aortic insufficiency due to rheumatic heart disease.The urine had a specific gravity of 1.020 and was otherwise normal. The hemoglobin was 11.5 gm/ 100 ml, the white blood cell count 14,500/cu mm with 83% neutrophils and 17% lymphocytes, and the hematocrit 35%. A fasting blood sugar was 110 mg and the blood urea nitrogen 96 mg/100 ml. A battery of liver function tests gave results within the normal range.The serum sodium was 137 mEq, potassium 5.4 mEq,
