The severity of mitral regurgitation (MR) and tricuspid regurgitation (TR) was evaluated semiquantitatively by Doppler color flow imaging. The maximum MR area/body surface area (MRA/BSA) correlated significantly to the severity of angiographyic changes (tau=0.897). The maximum TR area/body surface area (TRA/BSA) also correlated significantly to the severity in angiography (tau=0.874). The cutoff values were 0.5, 2, 4, and 8cm²/m² for MRA/BSA and 1, 2.5, 5, and 10cm²/m² for TRA/BSA. Fourteen children (mean age 4.2 years) underwent repair of partial atrioventricular septal defects (P-AVSD) from 1985 to 1992. The cleft in the anterior leaflet was closed in the mitral valve; other procedures such as annuloplasty were not performed. They have been followed for periods from 7 months to 7 years and 5 months (mean 4 years); they were examined by echo cardiography and the Holter electrical cardiogram at the end of the period. MR had reduced to grade 0-II in all cases. No patients were given any medication, and all remained in NYHA Functional Class I. Paroxysmal supraventricular tachycardia developed in only one patient. We concluded that no annuloplasty in mitral valve is needed in children suffering from P-AVSD.