The feasibility of the reaction of poly(oxyethylene phosphonate) 1 with chloroacetone under phase-transfer catalysis conditions for the preparation of poly(oxyethylene phosphonate)s bearing alpha-hydroxyl and oxirane groups in the side chains has been investigated. It has been established that the first stage of the reaction involves addition of the P-H to the carbonyl bond of chloroacetone resulting in poly(oxyethylene alpha-hydroxy phosphonate). During the second stage of the reaction, the oxirane formation proceeds via elimination of chloride ion. It is possible to direct the reaction to produce poly(oxyethylene phosphonate) 2, bearing 86.2% alpha-hydroxyl groups, or to poly(oxyethylene phosphonate) 3, bearing 91% oxirane groups. The structure of the products has been proved by means of H-1, C-13 and P-31 NMR spectroscopy. Thus design poly(oxyethylene phosphonate)s bearing alpha-hydroxyl and oxirane groups are of interest as polymer-carriers of drugs and polymers with their own bioactivity. The cytotoxicity of poly(oxyethylene phosphonate), poly(oxyethylene phosphonate)s bearing alpha-hydroxyl and oxirane groups has been studied. (C) 2003 Elsevier Science Ltd. All rights reserved.