Abstract: This invention provides a method of detecting whether a subject is predisposed to, or afflicted with, pulmonary arterial hypertension (PAH) which comprises (A) obtaining a suitable sample comprising a nucleic acid encoding bone morphogenetic protein receptor II from the subject; and (B) detecting in the nucleic acid encoding bone morphogenetic protein receptor II whether a mutation is present which is not present in a nucleic acid encoding wildtype bone morphogenetic protein receptor-II. This invention also provides a method of detecting whether a subject is predisposed to, or afflicted with, pulmonary arterial hypertension (PAH) which comprises (A) obtaining a suitable sample comprising bone morphogenetic protein receptor II from the subject; and (B) detecting in the bone morphogenetic protein receptor II whether a mutation is present which is not present in wildtype bone morphogenetic protein receptor-II.