Previously it was mentioned on this website and on www.pyramidpolymers.com that iodine and potentially HI (amongst other initiators) appear to be capable of inducing the living polymerization of a variety of monomers. Upon review of some data more evidence of the potential for the first truly living aqueous cationic polymerization have emerged (Table 1). When polymerization has little chain transfer both the apparent and theoretical number average molecular weights (Table 1, entry 2) show little discrepancy. Doubling of the reaction time leads to a doubling in polymer yield (Table 1, entry 5); however, the apparent molecular weight is lower than the theoretical. These results indicate that the number of active species are preserved throughout polymerization even after very long reaction times (i.e., days) albeit there is some chain transfer that occurs. As we mentioned earlier, a number of approaches can be used to help suppress the impact that such side reactions have and thus give rise to well-defined polymers.