Cationic copolymerization of methyl glyoxylate (GM), an aldehyde containing an ester group in addition to aldehyde function, with cyclic acetal, 1,3-dioxolane (DXL), was studied. Resulting copolymers after hydrolysis of the eater groups provide hydrophilic, degradable polymers containing ionic functions. It has been shown that despite the reversibility of homopropagation steps for both comonomers the conversion of both comonomers in copolymerization can be nearly quantitative. Molecular weights of copolymers are relatively high (up to 1.7 x 10(4)), although lower than that calculated for polymerization proceeding without transfer. It Nas established that chain transfer involves hydride ion abstraction from the GM monomer or from the GM repeating unit of the copolymer. Polymerization is accompanied by extensive chain transfer to polymer (transacetalization). Intramolecular reaction (backbiting) leads to formation of a cyclic fraction, of which the major component (the only one observed) is a heterodimer, in other words, a seven-membered cyclic acetal composed of one GM and one DXL unit. Intramolecular chain transfer to the polymer leads to redistribution of comonomer units, and copolymers having nearly random distribution are formed (with a slight tendency for alternation due to the steric repulsion between bulky substituents in the GM-GM homodiads).