A process for the preparation of chloropyrimidines of the formula ##STR1## in which the substituents may be alkyl, cycloalkyl, aryl or radicals containing heteroatoms, but in which at least one of the substituents R.sup.1 to R.sup.4 must be Cl, which involves:reacting a hydroxy-pyrimidine or its tautomeric keto form with phosphoryl chloride in the presence of an amine or amine hydrochloride;recovering phosphoryl chloride after the reaction by adding phosphorus pentachloride and distilling the phosphoryl chloride; andseparating the chloropyrimidine from the amine hydrochloride by addition of a solvent which will dissolve the chloropyrimidine but not the amine hydrochloride and removing the amine hydrochloride.