Controlled cationic polymerization of p-(chloromethyl)styrene (CMS) was achieved with an alcohol [CH3CH(Ph)OH] as an initiator and a highly oxophilic Lewis acid, BF3.OEt2, as an activator/catalyst. The polymerization is initiated by the BF3-mediated selective activation of the C-O bond of the alcohol and proceeds via a similar activation of the resulting similar tosimilar toC-OH dormant polymer terminal to give linear polymers without branched structures that would form via reactions of the chloromethyl pendent groups. Addition of a small amount of water retarded the polymerization to give controlled molecular weights that increased with conversion and were close to the calculated values for living polymers. Additional use of tetrabutylammonium hydroxide (n-Bu4NOH) as a hydroxide anion source further narrowed the molecular weight distribution (M-w/M-n = 1.5-1.8). Copolymerization of CMS and styrene or p-chlorostyrene with the BF3-based system also gave copolymers with controlled molecular weights. This is the first example of controlled cationic polymerization of CMS without concurrent side reactions of the chloromethyl functional groups. The success owes to the use of highly oxophilic BF3.OEt2 in conjunction with an appropriate alcoholic initiator.