Background- Growing use of the left ventricular(LV) systolic(LVSIsys) and diastolic synchronicity indexes(LVSIdia) in selecting potential responders to cardiac resynchronization therapy(CRT) has created a need for normative reference values. This study sought to determine reference ranges for TDI-derived LVSIsys and LVSIdia, and to assess their relations to age and conventional parameters reflecting LV systolic and diastolic functions. Methods and Results- We enrolled 160 completely healthy volunteers (45짹13yrs, 104 men) free of any disease. Maximal difference and SD of time to peak systolic and early diastolic velocities for LVSIsys and LVSIdia were measured using 6- and 12-segment models. Aging was not found to significantly change LVSIsys, whereas LVSIdia progressively and consistently increased with age. Significant correlations were observed between LVSIdia and parameters representing LV diastolic function, i.e. early mitral inflow velocity and its deceleration time, and early mitral annulus velocity. A physiologic rise in LV mass/Ht2.7 showed a weak, but significant correlation with LVSIdia(r=0.15 to 0.22), but not with LVSIsys. On multivariate analysis, age-dependent increase in LVSIdia was confirmed. Conclusions- Age-specific reference ranges for LVSIsys and LVSIdia are presented here. LVSIsys remain stable throughout age groups, whereas LVSIdia progressively increases with age. These data will be useful for defining abnormal LV synchronous contraction and relaxation, and help better select patients likely to respond favorably to CRT.