Aqueous dispersions of UV absorbing s-triazine compounds comprising (a) 5 to 50 percent by weight of an s-triazine compound of formula ##STR1## wherein R, R.sub.1, R.sub.2 and n are as defined in claim 1, and (b) 0 to 18 percent by weight of an anionic compound, and (c) 0 to 18 percent by weight of a nonionic compound, with the proviso that at least one of components (b) and (c) must be present. These dispersions are excellent formulations for enhancing the lightfastness of dyeings on synthetic fibers, especially on polyester or acid-modified polyester fibers.