A method of dyeing or printing cationically dyeable fibers, tannin-treated cellulose materials, paper, silk or leather, which comprises applying to said cationically dyeable fiber, tannin-treated cellulose material, paper, silk or leather at least one 4,5-dihydro-1H-1,2,3-triazolium compound of the formula (I) ##STR6## in which R.sup.1 and R.sup.2 independently of one another denote C.sub.6 -C.sub.4 -aryl or a heterocyclic radical having up to 3 rings and up to 4 heteroatoms from the series consisting of O, S and N,
- R.sup.3 and R.sup.4 independently of one another denote hydrogen, C.sub.1 -C.sub.12 -alkyl, C.sub.2 -C.sub.12 -alkenyl, C.sub.4 -C.sub.8 -cycloalkyl, C.sub.7 -C.sub.17 -aralkyl, C.sub.6 -C.sub.14 -aryl or nitrile or
- R.sup.3 and R.sup.4 together denote a 2- to 5-membered C bridge, which can optionally be interrupted by up to two oxygen or nitrogen atoms, and
- X.sup.- denotes an anion,
- wherein all the alkyl, alkenyl, cycloalkyl, aralkyl and aryl radicals and fused and heterocyclic radicals present can be unsubstituted or substituted by nonionic substituents, carboxyl groups, ammonium groups or pyridinium groups.