An analysis of the diffusion and kinetics in an enzyme-modified microcylinder electrodes is presented. A simple approximate analytical expression of concentration is derived for the cases where the enzyme is immobilized in a metallically conducting, or a non-conducting matrix. This is done by using Homotopy perturbation method. A closed approximate analytical expression of current is also reported in terms of all dimensionless parameters for film thickness (r(1)/r(0) = alpha), enzyme kinetics (chi r(0)) and for all values of Michaelis-Menten constant (K-M). Available limiting case results are compared with our results and are found to be in good agreement. The model is also extended to the chemical sensor case, of a conducting polymer without enzyme. (C) 2010 Elsevier B.V. All rights reserved.