Linear poly (ethylenimine)(, LPEI) was modified by attachment of 3-(dimethylferrocenyl) propyl groups to ca. 17% of its nitrogen atoms to form a new redox polymer for use as an anodic mediator in glucose/biofuel cells. The electrochemical properties of this polymer were compared to those of 3-ferrocenylpropyl-modified LPEI. When or was mixed with glucose oxidase and cross-linked with ethylene glycol diglycidyl ether to form hydrogels on planar, glassy carbon electrodes, limiting catalytic bioanodic current densities of up to at were produced. The use of dimethylferrocene moieties in place of ferrocene moieties lowered the of the films by and significantly increased electrochemical and operational stabilities. was shown to be the more effective polymer for use in biofuel cells and, when coupled with a stationary cathode comprised of laccase and cross-linked as a mediator, produced power densities of up to at. Power density increased to when a rotating biocathode was used. The stability of the biofuel cells constructed with was higher than that of the cells using.