An immunosensor for the rapid, sensitive and selective detection of generic Escherichia coli in water samples was developed on the basis of surface plasmon resonance (SPR). Antibodies against E coli were immobilized on a sensor surface and water samples with different concentrations of E coli were injected to the flow cell. The changes in the response unit (RU) due to the binding of different concentrations of bacteria were computed and a linear correlation (R-2 = 0.976) was obtained between log E coli concentration and the change in the RU with a working range of 9 x 10(1) and 1.8 X 10(5) cfu ml(-1). The complete regeneration of the sensor surface was realized by using 1% SDS solution. The selectivity of the developed sensor was examined with Enterobacter aerogenes and Enterobacter dissolvens which did not produce any significant response. The ability of the developed sensor to detect E coli in real water samples was investigated and the results were closed to that obtained from plate counting method. Based on these results, the developed immunosensor can be employed for rapid, label-free, sensitive and selective detection of E coli in water samples. (c) 2007 Elsevier Ltd. All rights reserved.