In this study, the specificity and the sensitivity of the immunomagnetic separation (IMS) technique were determined in a model system. The efficiency of the conventional cultural method (USDA) with and without IMS was compared both in spiked and naturally contaminated foods. Both methods were used to isolate Escherichia coli O157:H7 from 111 food samples sold in markets of Ankara, Turkey. In an evaluation using 8 spiked food samples, the conventional cultural method with IMS showed no difference in performance. The result of the analysis of 103 naturally contaminated foods showed that the conventional cultural method with IMS enabled the detection of 3 (2.9 %) EHEC positive samples whereas the conventional cultural method without IMS detected only one (0.9 %). Although poultry products are not believed to be a potential source of EHEC, we did isolate this pathogen in 2 of 57 poultry products by conventional cultural method with IMS.