The electrochemical properties of methylene blue immobilized on cellulose surfaces modified with titanium dioxide and titanium phosphate were investigated by cyclic voltammetry. The materials synthesized were incorporated into carbon paste electrodes. The electron mediator property of the methylene blue was optimized using a factorial design, consisting of two levels and three factors. The factorial analysis was carried out by searching for better reversibility of the redox process, i.e. the lowest separation between positive and negative peak potentials and a current ratio near unity. The pH does not appear to influence the reversibility of electron transfer but electrolyte concentration and type of modified cellulose surface are important for this chemically modified electrode system. The experimental observations and data analyses indicate that a 0.5 mol 1(-1) NaCl solution and the cellulose surface modified with titanium phosphate at either a pH of 4.0 or 7.0 are optimal conditions for this system.