This invention relates to new 2(1H)-quinolinone compounds having the formula: ##STR1## wherein R.sup.1 is a imidazopyridyl, thiazolyl, indolyl, dihydroindolyl, imidazolyl, benzimidazolyl, quinolyl, isoquinolyl, quinazolinyl, dihydroisoquinolyl, tetrahydroimidazopyridyl or tetrahydroquinolyl, each of which may be substituted with substituents(s) selected from the group consisting of lower alkyl, halogen, lower alkoxy, lower alkylthio, ar(lower)alkoxy, cyano, nitro, amino, lower alkylamino, acylamino, hydroxy and oxo,R.sup.2 is hydrogen, lower alkyl or halogen,A is a single bond or a group of the formula selected from the group consisting of: ##STR2## and --X--CO--, in which X is a single bond or lower alkylene andX.sup.1 is lower alkylene, and a heavy solid line means a single or a double bond,and its pharmaceutically acceptable salt. Said compounds are used in the therapeutic treatment of heart diseases and hypertension in human beings and other animals.