This paper describes an impedimetric method for monitoring the formation of bacterial biofilms on the surface of platinum and gold electrodes and its application for the indirect detection of bacteriophages. Impedance spectroscopy measurements showed that the biofilm capacitance, C-biofilm, the parameter of the electrical circuit which modelled the biofilm growth, was sensitive both to the biofilm growth and to its degradation as a consequence of the bacteriophage infection. Impedance results were compared with optical and confocal microscopy studies showing a good correlation. These results guarantee further work in this area to develop portable devices for the detection of bacteriophages. (C) 2008 Elsevier Ltd. All rights reserved.