Objectives: Left ventricular (LV) torsional deformation based on the helical myocardial fiber architecture, is due to oppositely directed apical and basal rotation, has been proposed as an important component of LV performance, but is difficult to measure. Recently, a novel ultrasound speckle tracking imaging (STI) method was introduced and proposed as a promising new method to assess LV torsional deformation. And, there is no study on the normal LV torsional function in children. Methods: LV torsional function by STI was assessed in 70 healthy children (mean age 7.0 짹 4.1, range 3 mo–16 yrs). LV torsion was defined as the net difference of LV rotation at the basal and apical planes. Counterclockwise LV rotation as viewed from apex was expressed as a positive value. Results: The mean peak basal and apical rotation was –4.33 짹 2.76째 and 14.5 짹 4.8째. The mean peak LV torsion and torsional velocity was 18.2 짹 6.1째 (3.1 짹 1.3째/cm, normalized by LV length) and 2.49 짹 0.88 rad/s (0.43 짹 0.21 rad/s/cm). The mean time to peak LV torsion and torsional velocity (% systolic time) was 96 짹 6% and 54 짹 14%. The mean peak LV untwisting velocity was –2.75 짹 1.12 rad/s (- 0.47 짹 0.24 rad/s/cm, normalized by LV length) and occurred at 15.7 짹 10.1% of diastolic time. The mean LV untwisting during isovolumic relaxation time (IVRT) was -3.7 짹 2.6째 (21 짹 16% of peak LV torsion (A)). Isovolumic untwisting recoil rate (A/IVRT) was 0.60 짹 0.38%/ms. The peak LV torsion, apical rotation, peak LV torsional velocity, and peak LV untwisting velocity (all normalized by LV length) decreased with age. Conclusion: The present study assessed firstly LV torsional function in healthy children using STI. Ultrasound STI is a promising new method to assess LV torsional deformation. The data in this study could be a useful reference for studying LV function in clinical and research pediatric cardiology.