A general procedure is presented for the preparation of cationic starch through a process of selective and controlled oxidation of starch by NaIO//4 treatment and subsequent reaction of the oxystarch (dialdehyde starch) with pyridinium acetohydrazide chloride (Girard's reagent P). Incorporation of cationic moiety into the dialdehyde starch was dependent upon the mole ratio of Girard's reagent P used and aldehyde groups generated into the starch substrate. Higher incorporation of cationic moiety rendered starch more readily soluble in water. The cationic starch derivatives produced were characterized viscometrically and conductometrically. The suitability of samples of low degree of cationation as paper sizing agents was evaluated.