Vic-triazole compounds of the formula ##SPC1##WhereinX and Y stand for O or NR,R.sub.1 stands for a mononuclear aromatically carbocyclic or aromatically heterocyclic radical,R stands for hydrogen, a (possibly substituted alkyl, aralkyl, cycloalkyl, aryl or alkoxycarbonyl radical, andWherein the aromatic and heterocyclic radicals may contain further non-chromophoric substituents with the exception of the nitro-group, andA may additionally be fused by a 5- or 6-membered carbocyclic ring,Are useful as optical brightening agents for organic materials.