This letter describes how the irreversible attachment of bovine serum albumin (BSA) to films of plasma-polymerized maleic anhydride can be measured by an indirect antibody-binding assay and how this attachment appears to be strongly affected by the polymerization conditions. Surface plasmon resonance (SPR) was used to follow the binding of the antibody, anti-bovine serum albumin (aBSA), to protein-modified plasma-polymerized maleic anhydride films. It was found that BSA could be irreversibly bound to polymers made under pulse plasma conditions, but BSA did not bind to,polymers made under continuous wave conditions. Moreover, the degree of antibody binding, which is directly related to the quantity of BSA on the polymer, correlated with the plasma duty cycle (t(on)/t(on) + t(off)): lower duty cycle pulse plasma conditions gave greater BSA attachment. We speculate that BSA is being covalently bound to the polymer via the reaction of amine groups on lysine residues in BSA with the retained anhydride group functionality in the polymer.