A rare case of pure severe aortic regurgitation (AR) accompanied with congenital bicuspid aortic valve is presented. A 36-year-old female was admitted with rapid development of congestive heart failure. Examinations clarified severe AR with congenital bicuspid valve. Either calcification or vegetation on the valve was completely denied. At operation, both leaflets were apart from each other with a distance of 7 mm at the anterior commissura. A mechanical valve (Björk-Shiley 23A) was sutured and she has been well. Pathological study of the resected leaflets revealed neither calcium deposit nor finding of infection but collagenous fibrous tissue with focal mucinous degeneration. A few cases of AR with bicuspid aortic valve have been reported in patients of annuloaortic ectasia. The partial annular ectasia was suspected as the cause of solitary aortic regurgitation with bicuspid aortic valve in our case.