The frequency of idiopathic aortitis in a large surgical cohort was found to be 4.3%. Thoracic aorta aneurysm formation, in the absence of systemic illness, was the most common manifestation. In the setting of a cardiovascular surgery practice, aortitis may first become apparent only after pathologic evaluation of excised specimens. The appropriate medical treatment for patients with incidentally discovered aortitis is not known. Because 17% of our patients subsequently developed new aneurysms, we suggest that it would be prudent for patients with idiopathic aortitis identified at the time of surgery to be periodically evaluated for recurrent or persistent disease.