This paper describes the design and preparation of thin polymeric films that resist the adsorption of proteins and the adhesion of bacteria to an extent comparable to, or better than, self-assembled monolayers (SAMs) that present tri(ethylene glycol) groups. These polymeric films were prepared by the reaction of a polyamine, for example, poly(ethylenimine), with a SAM that presented interchain carboxylic anhydride groups, and by the subsequent conversion of the amino groups of the polymer to amido groups on reaction with acyl chlorides. Polyamines functionalized with acetyl chloride produced films that resisted the adsorption of protein and the adhesion of bacteria to a useful extent. Functionalization of the polyamine with acyl chlorides that were derivatives of oligo(ethylene glycol) resulted in films that were 1-10 times more resistant than those obtained by acetylation. The removal of hydrogen bond donor groups from the surface of the polyamines upon acylation seems to be important for the generation of films that resist the attachment of proteins and bacteria.