Recently two-dimensional (2D) speckle tracking echocardiography (STE) derived from right ventricular (RV) free wall has been shown to be a very useful tool for the estimation of RV performance. The purpose of this study was to examine whether RV basal free wall strain can detect increased mean pulmonary arterial pressure (mPAP) in patients with chronic thromboembolic pulmonary hypertension (CTEPH). We investigated a total of 126 patients with CTEPH (mean age, 56 ± 12 years). They underwent echocardiography and right heart catheter examination. 2D STE-derived longitudinal strain was measured by placing 2 regions of interests (ROIs) on the RV basal free wall in RV-focused apical 4-chamber view. Peak strain (RV-PS) was acquired between the 2 ROIs. Conventional echocardiographic RV parameters (RV fractional area change, RV myocardial performance index, tricuspid annular plane systolic excursion, tricuspid annular peak systolic velocity, and tricuspid regurgitant pressure gradient) were evaluated as well. Right heart catheterization was performed on the day following of echocardiographic evaluation. Among RV echo parameters, RV-PS showed the best correlation with mPAP (r = 0.75, P < 0.0001). Receiver operating characteristic analysis revealed that a cut-off value of RV-PS -20.8% could detect mPAP ≧ 25 mmHg (sensitivity 78%, specificity 93%, area under the curve 0.90, P < 0.001). RV basal free wall strain was a useful tool for the non-invasive detection of increased mPAP in patients with CTEPH.