Modelling and simulation of PEM fuel cell stack operation is developed in Simulink(R) environment and validated through experimental data. The present work is the starting point for the development of a user friendly and versatile tool aimed at controlling and optimizing the operation of a PEMFC stack; in addition, it could be of help in stack and BOP components design, for instance feeding and humidification systems, cooling circuit, temperature control logic and electrical interface. The constitutive equations used to model the FC stack operation are the fundamental equations of electrochemistry. First, the model is used to describe the behaviour of a single cell under steady-state conditions upon varying variables such as temperature, pressure and relative humidity of reactants; then, it is applied to simulate the operation of a stack configuration, including also fluid-dynamics aspects, thermal and kinetic behaviour of feed systems. In particular, thermal control modelling is based on a simplified approach where different heat removal mechanisms are accounted for in a separate way. In its present state, the simulation tool so developed allows a feasible investigation of some process variables influence on the FC stack performances. The stack modelling is tested against benchmark results obtained from a 300W 20-cell air-cooled stack under variable operative conditions. MEAs based on Nafion 112 and Carbon cloth GDLs developed ad hoc are assembled into each cell of the stack. Although the model is quite simple, these preliminary results point out that it may be an adequate tool to set design targets and support further steps of optimization. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.