Dyspnoea on exertion is the most common presenting symptom of pulmonary hypertension (PH), often a progressive and ultimately fatal condition. However, the presenting manifestations are protean, and more subtle features such hoarseness (caused by compression of the left recurrent laryngeal nerve) challenge master clinicians. Clinician scientists have refined the clinical classification in a manner that aids in accurate diagnosis and facilitates communication among healthcare providers and research investigators. Diagnostic algorithms emphasize confirmation and characterization of PH by catheterisation as well as differentiating between the current classes based upon essential and contingent diagnostic tests.