The use of commercial anti-Escherichia coli 0157-labelled magnetic beads was investigated to improve detection of E. coli 0157 by immunomagnetic separation (IMS) from a range of environments on a dairy farm. Immunomagnetic separation proved effective for separation of target cells from laboratory mixtures and during stress in sterile and non-sterile pond water. The IMS procedure was possible with a range of samples (water, faeces, slurry, grass and soil). Non-specific binding of non-target bacterial cells proved problematic in a number of sample types. However, indigenous E. coli 0157 cells were detected from samples with a high faecal load, and only with use of IMS. Data on the probable survival and spread of the organism around the farm environment are also discussed.