Background: Right ventricular function is a strong determinant of prognosis in severe pulmonary hypertension. Methods: The aim of this study was to evaluate the prognostic value of estimates of right ventricular function obtained by echocardiography and Doppler tissue imaging and of functional class and 6-min walk distance (6MWD) in 142 patients with either pulmonary arterial hypertension (n = 104) or chronic thromboembolic pulmonary hypertension (n = 38). Echocardiography was prospectively performed, and demographics, medications, associated medical conditions, New York Heart Association class, and 6MWD at inclusion in addition to vital status, transplantation, and hospital admission related to pulmonary hypertension at follow-up were then collected by review of the medical records. Results: Variables associated with overall survival by univariate analysis were 6MWD (P = .009), functional class (P = .024), tricuspid annular plane systolic excursion (P = .03) and isovolumic peak velocity at the tricuspid annulus (IVCv) (P = .003). On multivariate analysis, IVCv (P = .015) and 6MWD (P = .016) were the only independent predictors of survival. Kaplan-Meier estimates of survival at 1 year were 95% in patients with IVCv > 9 cm/sec and 80% in those with IVCv <= 9 cm/sec (P = .002). Intraobserver and interobserver variability of IVCv measurement were 5% and 9%, respectively. Conclusions: Measurement of right ventricular function by Doppler tissue imaging, an easy, noninvasive, and reproducible method, is an independent predictor of clinical outcomes in patients with severe pulmonary hypertension.