Escherichia coli O157: H7 is an important human pathogen causing haemorrhagic colitis, haemolytic-uraemic syndrome and thrombotic thrombocytopenic purpura. In this study, 100 ground beef samples were collected randomly from beef markets in June 2004. For isolation of the bacteria, samples were firstly enriched in modified trypticase soy broth, followed by plating onto sorbitol MacConkey agar supplemented with cefixime and potassium tellurite. Consequently, the suspected non-sorbitol fermenting (NSF) colonies were confirmed by biochemical tests and employed for polymerase chain reaction (PCR) assay, using primers specific for O157 and H7 antigens gene. In this study, 7 NSF E. coli colonies were isolated; in PCR assay only one of them confirmed as E. coli O157: H7. The PCR assay employed in this study may be a possible alternative to immunological assays which detects somatic and flagellar antigens.