Abstract: The present invention relates to a process for the preparation of quaternary diesters of the formula: ##STR1## wherein X.sup.- represents a halogen atom, R.sub.1 and R.sub.2 are the same or different and are selected from an alkyl group having 1 to 3 carbon atoms or a hydroxyethyl group, or may be linked together to form an alkylene group having 4 to 6 carbon atoms which may be interrupted by an N atom or O atom, and R.sub.3 and R.sub.4 are the same or different and are selected from an alkyl group or alkenyl group having 8 to 22 carbon atoms, or may be linked together to form an alk(en)ylene group having 8 to 22 carbon atoms. In the processa) a secondary amine of the formula R.sub.1 --NH--R.sub.2 is gradually added to and converted with one or more liquid compounds of the formula ##STR2## a molar ratio in the range of 1.0:1.0 and 1.0:1.