Pulmonary hypertension (PH) is defined as a mean pulmonary artery pressure (mPAP) ≥25 mmHg, irrespective of etiology. In contrast to PH, the definition of pulmonary arterial hypertension (PAH) requires the exclusion of elevated pulmonary venous pressure, an established cause of PH, as reflected by a normal wedge pressure or left ventricular end-diastolic pressure (LVEDP) (≤15 mmHg). If PH is suspected in a patient, suitable screening tests are conducted to confirm the presence of PH and delineate the etiology to appropriately tailor an optimal therapeutic regimen. The diagnostic algorithm reflects an integration of assessment pathways that help differentiate patients with WHO groups II – IV of pulmonary hypertension from WHO group I PAH as well as the subgroups of PAH. Caution is advised to apply the algorithm to any individual patient as the evaluation process of any patient with suspected PH requires a variety of investigations intended to confirm PH and the specific PAH subtype and, once confirmed, evaluate the functional and hemodynamic impairments of those patients. Right heart catheterization is universally considered to be an indispensable part of the diagnostic assessment.