A straightforward synthesis of amphiphilic beta-cyclodextrin-poly(4-acryloylmorpholine) (beta-CD-PACM) polymers of controlled molecular weight, consisting of the radical polymerization of 4-acryloylmorpholine in the presence of 6-deoxy-6-mercapto-beta-cyclodextrin (beta-CD-SH) as chain-transfer agent, has been established. These derivatives carry a single beta-cyclodextrin (beta-CD) moiety at one terminus and their average molecular weight is in the order of 10(4). Thus, their beta-CD content is similar to 10% by weight. No evidence of un-functionalized PACM was found in the final products. The chain-transfer constant (C-T) of beta-CD-SH was found to be 1.30 by independently determining the reaction constants of both chain-transfer and propagation reactions. This ensures that the molecular weight, hence the beta-CD content of the polymers, does not significantly vary with conversion. These beta-CD-PACM polymers are highly soluble in water as well as in several organic solvents such as chloroform and lower alcohols. They proved capable of solubilizing in water poorly soluble drugs such as 9-[(2-hydroxyethoxy)methyl]guanine (Acyclovir) and of gradually releasing them in aqueous systems. (C) 2008 Wiley Periodicals, Inc.