The electrochemical behaviour of creatinine at the Keggin-type phosphomolybdate (PMo12)-doped polypyrrole (PPy) Film Modified glassy carbon electrode (PMo12-PPy/GCE) was studied. PMo12-doped PPy modified electrodes were achieved during the electrochemical preparation of the polymer films in aqueous solution. The redox behaviour of the modified electrodes was described by cyclic voltammetry. The electrochemical behaviour of creatinine at this modified electrode was studied by 0.5 order differential voltammetry. Numerous factors affecting the reduction peak currents of creatinine at the modified electrode were optimized to maximize the sensitivity. The experiment showed that creatinine had high inhibitory activity toward the reduction of modified electrode in 0.50 M H2SO4. The reduction peak currents of creatinine were linear related to logarithmic values of the creatinine concentration from 1.0 X 10(-6) to 1.0 X 10(-4) M with correlation coefficient of 0.9945, a detection limit of 5.0 x 10(-9) M of creatinine was estimated. The response mechanism of creatinine at PMo12-PPy modified electrode was discussed in detail. (c) 2005 Elsevier B.V. All rights reserved.