Escherichia coli O157:H7 lives in the intestines of healthy cattle, and can contaminate meat during slaughtering practices. Detection of the low infectious dosage of bacterium requires a sensitive method. We developed polymerase chain reaction (PCR) assays to detect the gene Stx2 irrespective of the bacterial serotype. In this study, the detection limit of the PCR protocol in detecting Stx2 in E. coli O157:H7 without prior enrichment was 103 CFU/ml, and with 4 h prior enrichment in modified tryptic soy broth was 102 CFU/ml. During a period of 7 months (December 2004 to June 2005), 154 slaughtered cattle at Shiraz slaughterhouse, were randomly selected and examined for surface carriage of E. coli O157:H7 via detection the Stx2 gene of verotoxigenic E. coli by PCR technique. E. coli O157:H7 was found in 14 of 145 (9.65%) feedlot cattle and in 1 of 9 (11.1%) dairy cull cows. This is the first report of the presence of E. coli O157:H7 in cattle from Iran.