Although the coronary arteries are so frequently involved in the general diseases of the vascular system, aneurysm is an extreme rarity. In the 116 years that have elapsed since Bougon1 (1812) reported the first case, after a careful search of the literature we have been able to collect only thirty-one examples of this condition—and at least two of these are extremely doubtful. This total does not include cases of periarteritis nodosa, a disease entity first described by Kussmaul and Maier2 in 1866. The multiple beadlike aneurysms of the coronary arteries, which are frequently present in this disease, are only part of a widespread involvement of the medium sized vessels throughout the body and are best considered from that standpoint. Few attempts have been made to collect the scattered case reports and to analyze them critically. The most elaborate of these are: Crisp3 (1871), eleven cases; Capps4 (1899), nineteen cases, and