Procedure for the preparation of cationic guar having DS comprised between 0.01 and 3, free from boron and suitable for the use in the cosmetic field and in household cleaning products, comprising the following steps: a) 100 parts by weight of guar flour are reacted with 3-chloro-2-hydroxypropyl trimethylammonium chloride and sodium hydroxide in from 5 to 500 parts by weight of a water and alcohol mixture containing from 20 to 50% by weight of water; b) the amount of water and alcohol is regulated in order to obtain a dispersion containing from 65 to 95% by weight of a of water and alcohol mixture containing from 30 to 50% by weight of water and the dispersion is maintained under stirring at temperature comprised between 15 and 40.degree. C. for at least 10 minutes; c) the mixture is filtered under vacuum and dried to obtain the purified cationic guar.