The aim of this study was to investigate presence of E. coli O157:H7 on rectal swabs and buffalo carcasses slaughtered in the abattoirs. Five abattoirs in Istanbul were visited between Januarry 2000 and 2001. During visits, systematic sampling method was used and a total of 28 buffalo and their carcasses were sampled. All the swabs were placed in modified E. coli broth containing Novobiocin. Immunomagnetic seperation (IMS) was performed after the preenrichment. The product from the IMS was used for further identification procedures using the Cefixime Tellurite MacConkey agar (CT-SMAC) agar, Chrom agar and biochemical tests. The reaction of the isolates with anti-O157 and H7 sera were also analysed. Seven isolates from the rectal swabs and 2 from the carcasses were sorbitol negative on CT-SMAC agar. None of these isolates reacted with antisera to E. coli O157 nd H7.