An analysis of the diffusion and kinetics in amperometric immobilized enzyme electrodes is presented for reactions of the enzyme and substrate. This analysis contains a non-linear term related to Michaelis-Menten kinetics. In this paper, we obtain approximate analytical solutions for the non-linear equations that describe diffusion and the reaction within the film by employing the homotopy perturbation method (HPM). The obtained analytical results are compared with the available limiting case results and found to be in satisfactory agreement. (C) 2010 Elsevier Ltd. All rights reserved.