Dyestuffs of the formula ##STR1## WHEREIN A denotes a ring which contains at least one quaternary nitrogen atom;B denotes an isocyclic or heterocyclic radical;Y denotes a radical for completing a ring;R denotes hydrogen or alkyl;An .sup.- denotes an anion; andk, m and n denote 1 or 2,Are suitable for dyeing and printing of natural and synthetic materials, particularly of polyacrylonitrile, copolymers of acrylonitrile with other vinyl compounds, of acid modified polyesters and acid modified polyamides. The dyestuffs are also useful in writing fluids, rubber stamp inks, ball point pen inks and in inks for flexographic printing.