Background: While the number of patients with aortic regurgitation (AR) has been increasing in the aging society, its etiologies remain to be fully elucidated. Methods: We studied consecutive 126 patients with chronic moderate or severe AR who underwent TEE. After the study subjects were divided into 2 groups by the age of 65 years, AR etiology was examined in each group. Results: In the older group (n = 85), cusp bending was the most frequent cause of AR (48.2%), and right coronary cusp (RCC) was the most common (90.2%). In the younger group (n=41), bicuspid valve was the most frequent cause (36.5%), and cusp bending was less frequent (16.5%). Multivariate analysis revealed that age was the only factor associated with cusp bending. Conclusion: Cusp bending of RCC was the most frequent etiology of AR in the elderly. Because AR caused by cusp bending has a possibility to be mended by aortic plasty, it is important to detect it by TEE especially in the older patients.