Abstractα‐Trifluoromethylstyrene (TFMST) does not undergo radical homopolymerization with azobis(isobutyronitrile) (AIBN) in bulk at 60°C. Low‐temperature initiation was not effective either. Radical copolymerization of TFMST (M2) with styrene (ST,M1) has yielded monomer reactivity ratios as follows:r1= 0.60 andr2= 0.00. It has been found that the cyclohexyl radical generated by reaction of cyclohexylmercuric chloride with sodium borohydride adds to the β‐carbon of TFMST 7.5 times faster than that of ST. Combination of the copolymerization analysis and the “mercury method” has allowed us to estimate Alfrey–PriceQandeparameters for TFMST to be 0.43 and 0.90, respectively. Thus, due to the strongly electron‐withdrawing effect of the trifluoromethyl group, this styrene is highly electron deficient. In spite of the favorable electronic effect, however, the ceiling temperature appears very low, presumably due to the