B-type natriuretic Peptide (BNP) is elevated in conditions with ventricular volume and pressure overload. The physiological, diagnostic and therapeutic role of BNP in right ventricular (RV) dysfunction and pulmonary arterial hypertension (PAH) are reviewed in this article. BNP levels can be used to differentiate between breathless patients with a respiratory disease and those with PAH. BNP has been shown to correlate with mean pulmonary arterial pressure and pulmonary vascular resistance in patients with PAH, whether primary or secondary. BNP is also a predictor of mortality in patients with primary pulmonary hypertension. These are important clinical implications in that a non-invasive blood test may be used to identify patients who require more invasive procedures (such as cardiac catheterization). There is increasing evidence that BNP or NT-proBNP measurements may also be used to guide therapy (e.g. pulmonary vasorelaxants) in PAH. Enhancement of the natriuretic peptide pathway has been shown to reduce cardiac hypertrophy and PAH and hence, there may be therapeutic potential via recombinant BNP or neutral endopeptidase inhibitors in RV dysfunction and PAH.