AbstractInsoluble polymers adsorbing bacterial cells were prepared by reactions of chloromethylated, divinylbenzene crosslinked polystyrene (CMPS) beads with poly(ethylene glycol) 600 (PEG600), PEG monolaurate (PEGLE), polyethylenimines (PEIs, MW = ca. 300. 600. and 1200, referred to as PEI300, PEI600, and PEI1200, respectively), as well as ethylenediamine (ED) and tetraethylenepentamine (TEP) as polyethylenepolyamines. CMPS‐ED and CMPS‐TEP were further quaternized with 1‐iodooctane (IO) and 1‐iodododecane (IDD), respectively. These polymers were brought into contact with Escherichia coli by stirring in sterilized, distilled, and deionized water. Although CMPS‐PEG and CMPS‐PEGLE did not adsorb the cells, they caused a decrease in the number of viable cells. The decrease seemed to result from the bactericidal action of substances leached from the polymers. CMPS‐PEI300, CMPS‐PEI600, and CMPS‐PEI1200, CMPS‐ED‐IO, and CMPS‐TEP‐IDD caused a decrease in the viable cell number by adsorption of the cells to their surfaces. It was observed with a scanning electron microscope that the cells were present on the surfaces of CMPS‐PEI600 beads. The decrease coefficient for decrease in viable cell number of E. coli caused by the polymer increased with nitrogen content of the polymer. The adhesion of the cells to CMPS‐PEI300, CMPS‐PEI600, and CMPS‐PEI1200, CMPS‐ED‐IO, and CMPS‐TEP‐IDD was due mainly to electrostatic interaction between them.