The syntheses of well-defined polystyrenes functionalized with a definite number (from one to four) of chloromethylphenyl groups at the chain ends or in the chains by means of anionic Living polymerization in conjunction with functional group transformation are described. The synthetic method involves the introduction of anion-stable methoxymethylphenyl or tert-butyldimethylsilyloxymethylphenyl groups at the chain ends or in the chains and subsequent transformation reactions of these groups into chloromethylphenyl groups with BCl3. It is also possible to transform the tert-butyldimethylsilyloxymethylphenyl group into bromomethylphenyl and iodomethylphenyl groups by treatment with Me3SiCl-LiBr, and Me3SiCl-NaI, respectively. Furthermore, the synthesis of well-defined polystyrenes having two, four, and six methoxymethylphenyl and six chloromethylphenyl termini via a new iterative approach using 3-(tert-butyldimethylsilyloxy)-1-propyllithium is described. It involves repeated chemical transformations at the chain end from tert-butyldimethylsilyloxybutyl, bromobutyl, and methoxymethylphenyl groups to the chloromethylphenyl group. At each stage in the iteration, the number of chloromethylphenyl groups doubles. The resulting polymers all, after HPLC fractionation in some cases, possessed well-controlled molecular weights and narrow molecular weight distributions. Their functionalities were nearly quantitative in all cases.