There are described rhodamine derivatives of the formula ##STR1## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each hydrogen or substituted or unsubstituted C.sub.1 -C.sub.4 -alkyl, or R.sup.2 is paired off with R.sup.5 or R.sup.4 with R.sup.6 to form 1,3-propylene, which can be substituted,R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are each hydrogen or methyl,R.sup.9 is hydrogen, substituted or unsubstituted C.sub.1 -C.sub.4 -alkyl or a radical of the formula (C.sub.2 H.sub.4 O--).sub.n H, where n is 2 or 3, andAn.sup..crclbar. is the equivalent of an anion derived from an addition or condensation polymer that contains acid groups, novel cyclic rhodamine dyes, and the use of the novel rhodamine derivatives and cyclic rhodamine dyes for dyeing polyacrylonitrile fibers, for incorporation into polymers or for preparing inks.