NOVELTY - A retarding method involves introducing a cementitious slurry comprising water, a cement and a water-soluble or water-dispersible set retarder into a wellbore. The set retarder comprises a copolymer of repeating units (I).    USE - Method for retarding the set time of a cementitious slurry introduced into a subterranean formation penetrated by a gas, oil or geothermal wellbore.    ADVANTAGE - The method enables delaying the hardening of the cementitious slurry when introduced into the subterranean formation until a downhole temperature greater than or equal to 500 degrees F, even in the absence of an intensifier.    DETAILED DESCRIPTION - A retarding method involves introducing a cementitious slurry comprising water, a cement and a water-soluble or water-dispersible set retarder into a wellbore. The set retarder comprises a copolymer of repeating units of formula ((-(E)c-)(-CH2-C(R1)-G-O-R2-XZ-)d(-F1)e-)(I), where the slurry is provided to harden to a solid mass.    E=polymerizable ethylenically unsaturated monomer, second monomer having alkoxylated sulfate, phosphate or ketonic salt, preferably acrylic acid, methacrylic acid (both preferred), acrylamide, methacrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, N-isopropylacrylamide, maleic acid or anhydride, fumaric acid, itaconic acid, styrene, sulfonic acid, vinyl sulfonic acid, isopropenyl phosphonic acid, vinyl phosphonic acid, vinylidene diphosphonic acid or 2-acrylamido-2-methyl-propane sulfonic acid;    G=alkoxylated monomer of formula (-CH2-C(R4)(R6-O-R5-R7)), -CH2- or -CH(CH3)-, preferably polyethylene glycol allyl ether, polypropylene glycol allyl ether, polyethylene glycol/propylene glycol allyl ether, hydroxyethyleneglycolmethyl methacrylate or methoxyethyleneglycolmethyl methacrylate;    R1,R4=H, straight or branched 1-4C alkyl;    R2,R5=hydroxyl substituted alkyl or alkylene having 1-6C, -(CH2CH2-O-) or -(CH2CH(CH3)-O-);    R6=-CR2- or -C=O;    R7=-H or 1-18C straight or branched alkyl or acetate;    X=anionic radical consisting of -SO3, -PO32- or -COO;    X=anionic radical of -SO3-, PO32- or -COO-;    Z=-H or water soluble cationic moiety that counterbalances the valence of the anionic radical;    n=1-150;    c=positive integer;and    d,e=0 or positive integers provided that d and e are not both 0.