Background: Assessment of right ventricular (RV) systolic function remains difficult because of the RV's complex shape. We aimed to evaluate RV systolic function objectively with two-dimensional strain (2DS) analysis in patients with acute pulmonary thromboembolism (PTE). Patients and methods: From March 2005 to June 2009, 48 consecutive patients with acute PTE were included in this study. After excluding six patients, three with atrial fibrillation, three with recurrent episodes of PTE and one with permanent pacemaker, the remaining 42 patients (17 males, mean age 67.3짹10.7 years) were analyzed. Results: Mean RV fractional area change (RVFAC) was 22.1짹9.1%; RV Tei index was 0.88짹0.28; tricuspid annular plane systolic excursion (TAPSE) was 1.58짹0.32 cm; and TR Vmax was 3.7짹0.4 m/s at the time of diagnosis. Global longitudinal 2DS of RV was markedly decreased (-12.3짹6.0%). After treatment, follow-up echocardiographic data were obtained from 33 patients (mean: 9.0짹7.5 days, duration: 1–34 days). Mean RVFAC (22.1짹9.1 to 40.9짹8.3%), RV Tei index (0.88짹0.28 to 0.50짹0.16), TAPSE (1.58짹0.32 to 2.2짹0.26cm/s) and TR Vmax (3.7짹0.4 to 2.6짹0.3m/s) were significantly improved (P<0.001). Global longitudinal 2DS of RV were also significantly improved (-12.3짹0.6 to -20.6짹4.4%, P<0.001). Global longitudinal 2DS of RV showed significant correlation with RVFAC (r=−0.558, P<0.001), TAPSE (r=−0.573,P<0.001) and RV Tei index (r=0.613, P<0.001). Conclusions: Global longitudinal 2DS of RV decreased in the patients with acute PTE and improved after stabilization. This value can therefore be used to assess RV systolic function in patients with acute PTE.