A series of new 6-[4-[[(aryloxy) acyl] amino] phenyl]-4, 5-dihydropyridazinones have been synthesized and evaluated as combined vasodilator/@-adrenoceptor antagonists and potential antihypertensive agents. Many of the early compounds displayed an unacceptably high level of intrinsic sympathomimetic activity (ISA) and a relatively short duration of action. Disubstitution in the 2, 3-positions or in the 4-position of the aryloxy ring gave compounds ...