The invention relates to a process for the preparation of activated chitosans, in which process a chitosan is reacted with an acid for salt formation, preferably followed by a reaction with a base. The addition of acid and the addition of bases which is preferably to be effected in the activation are carried out in a suspending agent which largely prevents the chitosan salts from dissolving, suitable suspending agents can be both aqueous solutions of inorganic salts and organic or aqueous-organic solvents. The invention also relates to a process for the preparation of both water-soluble and water-insoluble chitosan derivatives by reacting the activated chitosans with reagents which are generally suitable for the reaction of polysaccharides or amines.