Dihydropyridine derivatives and acid addition salts thereof which are of use as prophylactic or/and therapeutic drugs for cardiovascular diseases, said dihydropyridine derivatives having the formula ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are the same or different and each is alkyl, cycloalkyl, cycloalkylalkyl or alkoxyalkyl; R.sup.4 and R.sup.5 are the same or different and each is hydrogen, halogen, nitro, trifluoromethyl, alkyl, cycloalkyl, alkoxy, cyano, alkoxycarbonyl or alkylthio; R.sup.6 is hydrogen, alkyl, cycloalkyl, aralkyl, aryl or a pyridyl; X is oxygen, sulfur, vinylene, azomethine or a group of the formula ##STR2## A is alkylene; Ar is aryl or a pyridyl; m is an integer of 1 to 3; n is an integer of 0 to 2.