A method for thickening an acidic aqueous composition. The method is based upon the addition of a crosslinked cationic homopolymer of a cationic monomer of formula I ##STR1## in which: R is hydrogen, (C.sub.1-4)alkyl, or the radical CH.sub.2 COOH, R.sub.1 is hydrogen, methyl, carboxy, or the radical CH.sub.3 --CH.dbd.CH, R.sub.2 is methylene or a straight or branched (C.sub.2-4) alkylene moiety, R.sub.3, R.sub.4, and R.sub.5 are independently hydrogen or (C.sub.1-4) alkyl, and X is chlorine, bromine, iodine, hydrogen sulfate, or methosulfate to the aqueous solution in an amount ranging from about 0.01 to about 5% of the weight of the acidic aqueous composition. The homopolymers are crosslinked with a crosslinking agent containing at least two ethylenically unsaturated moieties present in amounts ranging from not less than 50 to about 600 ppm of the homopolymer total weight.