Objective To assess regional left ventricular systolic function in patients with hypertrophic cardiomyopathy (HCM) using real-time three-dimensional echocardiography (RT-3DE).Methods Twenty-five patients with HCM which was asymmetric septal hypertrophy,and twenty healthy subjects were enrolled in the study.The apical four-chamber view of left ventricular was acquired by RT-3DE.The left ventricular volume-time curves were analyzed quantitatively with Tomtec 4D LV-Analysis 3.0,and regional end-diastolic volume and end-systolic volume of left ventricular (rEDV,rESV),the time to minimum systolic volume (rESVT),regional stroke volume (rSV),regional ejection fraction (rEF),regional-global ejection fraction (rgEF) and the parameters of left ventricular dyssynchrony were measured.Results In the HCM group,the values of Tmsv16-Dif,Tmsv16-SD,Tmsv16-Dif％,Tmsv16-SD％ were significantly lower compared with the control group (P ＜ 0.01),and rEDV,rSV,rEF and rgEF in hypertrophic segments were lower than those in non-thickening and mild-thickening segments (P ＜0.05).In the control group,there were no significant difference of those parameters among all segments (P ＞0.05).The values of rEDV,rSV and rgEF in hypertrophic segments decreased in the HCM group (P ＜0.05),at the basal level,rEF in hypertrophic segments decreased,at the apical level,it increased,but the differences at the mid-ventricular level between the two groups were not significant;the values of rEF and rgEF in non-thickening and mild-thickening segments increased (P ＜0.05).Conclusions RT-3DE could sensitively detect left ventricular dyssynchrony and accurately assess regional left ventricular volume and function of different segments in patients with HCM.