Purpose : Recent development of 2-D speckle tracking echocardiography (2DSTE) made it possible to evaluate the long- and short-axis function of left ventricle (LV) by measuring longitudinal, circumferential, radial strain and strain rate of myocardium. The sequence of functional deterioration in each axis of progressively deteriorating LV is not well elucidated and this study was undertaken to investigate the serial changes of LV myocardial function in doxorubicin-treated murine hearts. Methods and results: Nineteen male rats (340.0짹33.9g) were assigned in group I (control, n=9) and group II (doxorubicin treated, n=10). Doxorubicin of 1.25mg/kg was intraperitoneally administered every other days in group II (Total amount : 20mg/kg) and equivalent dose of normal saline was administered in group I. Echocardiography was taken at baseline, 1st, 2nd, 4th, 6th and 8th week and left ventricular volume, ejection fraction(LVEF), fractional shortening (FS), longitudinal strain/strain rate(SL/SrL), circumferential strain/strain rate(SC/SrC) and radial strain/strain rate(SR/SrR) with 2-DSTE were obtained. After the echocardiographic examinations at 8th week, intracardiac catheterizations were performed under general anesthesia and dP/dt-max were acquired in all rats. At baseline, there was no difference in body weight and echocardiographic parameters between groups. At 2nd week, SrL and SC were impaired prior to other parameters compared with baseline (-4.3 vs -3.8cm/s, p=0.024, -18.8 vs -16.5%, p=0.011). At 4th week, LVEF and SL began to deteriorate (81.0 vs 71.3%, p<0.01, -15.9 vs -13.6%, p=0.050). At 6th week, SrC was impaired (-5.3 vs -4.1cm/s, p<0.01). At 8th week, FS, SR and SrR were impaired in group II. (49.0 vs 34.3%, p=0.001, 55.4 vs 38.1%, p=0.010; 7.8 vs 6.6cm/s, p=0.041). In group I, there was no change in strain rate, strain and LVEF at 8th week. dP/dt-max was correlated with only FS and SR in group II (r=0.673, p=0.033; r=0.782, p=0.008, respectively), not with SL, SrL, SC, SrC or LVEF in group II. Conclusions : The sequence of functional deterioration in doxorubicin treated murine heart was as follows; SrL and SC at 2nd week, LVEF, SL at 4th week, SrC at 6th week, SR, SrR and FS at 8th week. At the time of full-blown functional impairment at 8th week, dP/dt-max was correlated with only FS and SR. These findings suggested that long axis function of LV is impaired before short axis function during the development of heart failure. By analyzing long axis function of LV by 2-D speckle tracking echocardiography can serve as a useful tool in early detection of doxorubicin induced cardiomyopathy