We examined the effects of beta-adrenoceptor antagonists, propranolol and pindolol, on hypoxic pulmonary vasoconstriction using isolated, blood-perfused dog lung lobes. Pindolol markedly inhibited the development of hypoxic pulmonary vasoconstriction, whereas propranolol had no effect. The different role of the drugs on hypoxic pulmonary vasoconstriction is discussed.