This paper describes an approach for quantifying low concentrations of bacteria, particularly Escherichia coli, based on the measurement of the initial attachment of bacteria to platinum surfaces, using impedance spectroscopy. The value of the interface capacitance in the pre-attachment stage (before 1 min of attachment) showed correlation with suspended concentration of bacteria from 10(1) to 10(7) CFU mL(-1) (colony fort-ning units per mL). This method was found to be sensitive to the attachment time, to the applied potential and to the size of the counter electrode. The sensor lifetime was also evaluated. (C) 2008 Elsevier B.V. All rights reserved.