Triazine derivatives of formula (1) wherein R.sub.1 is C.sub.1 C.sub.20alkyl; C.sub.3 C.sub.7cycloalkyl; or C.sub.1 C.sub.20perfluoroalkyl; R.sub.2 is hydrogen; C.sub.1 C.sub.20alkyl; or C.sub.3 C.sub.7cycloalkyl; and R.sub.3 is hydrogen; C.sub.1 C.sub.20alkyl; C.sub.3 C.sub.7cycloalky; C.sub.1 C.sub.20perfluoroalky; C.sub.1C.sub.20alkyl-carbonyl; C.sub.3 C.sub.7cycloalkyl-carbonyl; C.sub.1 C.sub.20perfluoroalkyl-carbonyl; or phenylcarbonyl; are described. The compounds exhibit pronounced action against gram-positive and gram-negative bacteria and also against yeasts and moulds. They are also suitable for treating or preventing biofilms on human tooth surfaces and oral mucosa ##STR00001##