Aims: To study the presence, numbers and virulence profiles of Escherichia coli O157 in sheep faeces and validate the microbiological methods used to attain these data. Methods and Results: Flock level prevalence was found to be 40% ( six from 15) and 6(.)5% of faecal samples tested were found to be positive. Two farms gave samples defined as high shedding (>10(4) CFU g(-1)), one of which comprised 91% positive samples with 13/33 at the high shedding level. Conclusions: These data confirmed that sheep are an important reservoir of E. coli O157. Significance and Impact of the Study: Sheep play a significant role in the maintenance and dispersal of E. coli O157 in the farming environment and are an important source of human infection.