Chloro-bis(alkylamino)-s-triazines are prepared by step-wise replacement of two chlorine atoms of cyanuric chloride with alkylamino groups.Cyanuric chloride, an inorganic base and an alkylamine are continuously fed to a first tubular zone in stoichiometric proportions and reacted therein under turbulent conditions, at an elevated temperature not exceeding 90.degree. C., and for a short reaction time, and the reaction product is continuously fed to a second tubular reaction zone together with stoichiometric quantities of inorganic base and of a second alkylamine, and reacted therein with the latter at an elevated temperature not exceeding 100.degree. C., under turbulent conditions and for a short reaction time.