Authors reviewed and analyzed 108 cases of secundum ASD(1–15 years old), which had been diagnosed bycineangiography in Seoul Natinal University Children's Hospital from 1979 to 1985. 1) The incidence of theasociation of MVP with secundum ASD was 48%(Male 43%, Female 52%). 2) The incidnece of this association incresedwith age(1–5 years old: 39%, 6–10 : 50%, 11–15: 59%). 3) The incidence of concurrent mitral regurgitation in MVPassociated with ASD was 48%. No special correlation was not found between the degree or incidence of MVP and thatof MR. 4) The incedence of the association of MVP with ASD increased with the increaseing amount of leftventricular geomatry attendant on left to right shunt (QS/QS < 2:33%, 2<=QP/QS < 4:52%, QP/QS >= 4: 100%). Thissuggested that abnormal left ventricular geometry attendant on left to ring shunt would contribute much to theassociation of MVP with secundum ASD.