Artificial self-purification (depuration) of mussels (Mytilus deulis) was undertaken at three temperatures, under conditions similar to those likely to be experienced in the commercial shellfish industry of the UK. During a 72 h depuration period, samples of mussel flesh were examined for three faecal indicator bacteria, Escherichia coli, Group D faecal streptococci and sulphite-reducing Clostridium spores, and two types of bacteriophage. There was a statistically significant difference in the elimination rate of faecal indicator bacteria compared with the slower rate for both bacteriophages.