A general mathematical model describing the response of an array of flat amperometric electrodes with arbitrary size and spatial distribution at the bottom of a measuring cell with rectangular walls and finite dimensions is outlined. It is based on the three-dimensional diffusion equation with initial and boundary conditions corresponding to the physical situation which was numerically solved by the implicit alternating-direction finite-difference method. The accuracy of the numerical solution was confirmed by theoretical and experimental results obtained by other authors. By comparing the chronoamperometric curves of the individual electrodes and by examining the spatial concentration distribution in the measuring cell conclusions can be drawn concerning the mutual influence of the individual electrodes for a given geometry of the array and the dimensions of the measuring cell. This will allow the designing of arrays and selecting the proper measuring cell dimensions resulting in minimal sensor interferences. Chronoamperometric curves show the time required for attaining quasi steady state and the corresponding current value. Illustrative examples are presented.