Reactivities of polychloroalkanes as telogen agents in redox telomerization and initiators in atom transfer radical polymerization (ATRP) are compared. Activation of tri- and tetrachloroalkanes in redox telomerization catalyzed by copper salts is reviewed. In ATRP, both kinetics and chain end structures depend on relative reactivities of several potential initiation sites. On the basis of a ¹³C and ¹H NMR analysis, different mechanisms of activation and reactivity orders are proposed. It appears that carbon tetrachloride is a bifunctional initiator for both styrene and MMA polymerizations catalyzed by the copper (I) chloride / 2,2` - bipyridine complex. Trichloroalkanes bearing an electron-withdrawing substituent in the α-position to the trichloromethyl group are also at least bifunctional initiators in styrene polymerization. ATRP is finally regarded as an extension of redox telomerization to a polymerization process.