We have rarely observed the appearance of a dissection of the aortic sinus of Valsalva during catheterizations of the related coronary artery. The aim of this study is to describe the cause, mechanism, and evolution of this complication, which have implications for the management of the patient. According to our experience (one case out of 12,546 diagnostic and three cases out of 4,970 angioplasty procedures performed during the last 6 years), the dissection of the sinus of Valsalva always results from the retrograde extension of a dissection of the right coronary artery. It usually remains localized, but it may quickly involve the entire aorta. Contrast injections and balloon inflations promote its propagation, so these procedures should be avoided if possible. Instead of angiography, transesophageal echocardiogram is a safe and accurate method for studying its extension and as a follow-up method. The sinus of Valsalva dissections that remain localized during catheterization tend to spontaneously resolve in the first month.