Six patients undergoing aortic valve replacement had rare or unusual causes of isolated, pure aortic regurgitation. Two patients had congenitally bicuspid aortic valves with a false commissure (raphe) displaced to the aortic wall ("tethered bicuspid aortic valve"), two had floppy aortic valves, one had a congenital quadricuspid valve, and one had radiation-induced valve damage.