Left heart disease (LHD) is probably the most frequent cause of pulmonary hypertension (PH). Although in the past, rheumatic mitral valve stenosis has been the most common cause of this condition, PH-LHD mainly results from heart failure related to systolic and/or diastolic dysfunction of the left ventricle (LV) and is associated with elevated left-sided cardiac filling pressures. Most patients have a passive increase in pulmonary arterial pressure (Ppa) due to backward transmission of the elevated left atrial pressure, while a small subset develop severe PH with elevated transpulmonary gradient (TPG) and pulmonary vascular resistance (PVR). When present, PH is usually associated with a poor prognosis and increased mortality. Optimising heart failure regimens and corrective valve surgery are the cornerstones of the treatment of PH in LHD. Although PH-LHD may evolve to right ventricular (RV) failure and is associated with some changes in the pulmonary vascular bed similar to pulmonary arterial hypertension (PAH), there are no data to support the use of PAH-specific therapies in the setting of PH-LHD. However, recent studies have suggested the usefulness of sildenafil, a phosphodiesterase type-5 inhibitor (PDE-5 I). This chapter addresses the epidemiology, pathophysiology, risk factors and treatment controversies of PH-LHD.