Anti-allergic 4-benzyl-1-(2H)-phthalazinone derivatives of the formula in which R1 denotes fluorine, chlorine, bromine, trifluoromethyl, C1-C6-alkyl, hydroxyl, C1-C6-alkoxy, C2-C6-alkanoyloxy, amino, C1-C6-alkylamino, di-C1-C6-alkylamino, C2-C6-alkanoylamino, C2-C6-alkanoyl-C1-C6-alkylamino or a nitro group, R2 is hydrogen or has one of the meanings indicated for R1, where R1 and R2 can be identical or different, the radicals R3 and R4 are identical or different and denote hydrogen, halogen, C1-C6-alkyl, hydroxyl, C1-C6-alkoxy, benzoyloxy or C2-C6-alkanoyloxy and A is an azacycloalkanyl radical. |