The normal mean pulmonary artery pressure (PAP) is 14 ± 3 mmHg. Precapillary pulmonary hypertension is defined as a mean PAP ≥ 25 mmHg at rest and a pulmonary capillary wedge pressure ≤ 15 mmHg as assessed by right heart catheterization. When performed in experienced centers, right heart catheter procedures in patients with pulmonary hypertension are associated with low morbidity and mortality rates. Right heart catheterization remains essential for the management of pulmonary arterial hypertension (PAH) as it confirms the diagnosis, determines the type of pulmonary hypertension, its severity, its vasoreactivity as well as response to therapeutic interventions. The hemodynamic severity largely influences patients' management including the choice of initial and subsequent therapies. Hemodynamic evaluation during exercise allows a precise characterization of the true resistive properties of pulmonary vessels through the assessment of the pressure-flow relationship. The significance of isolated pulmonary hypertension during exercise remains unknown. Indeed, roughly 50% of healthy subjects > 50 years old exhibit mean PAP > 30 mmHg during mild exercise. Isolated exercise-induced increases in mean PAP > 30 mmHg during exercise is thus no longer used to define pulmonary hypertension. More complex hemodynamic parameters allow partitioning of arterial and venous vascular resistance, as well as a better characterization of pulmonary artery compliance, right ventricle function and right ventriculo-arterial coupling. The clinical relevance of these subtle markers of pulmonary vascular abnormalities remains unknown.