Postmortem examinations on 160 otters found dead in Great Britain from 2005 to 2007 showed a high prevalence of infection with the bile fluke Pseudamphistomum truncatum in otters from Somerset and Dorset but no infection in otters from other areas, including Cornwall, the western half of Devon, northeast England and Scotland. Cases were also recorded for the first time in Gloucestershire and East Anglia. Eighteen of the 28 infected otters were male and no cubs were infected, but there was no significant correlation between infection status and sex or age. There was a strong positive correlation between bile fluke infection and gall bladder pathology. Thirty otters had thickened gall bladders resulting from hyperplasia of the epithelial and smooth muscle layers, fibrosis and infiltration by inflammatory cells and 19 of these were infected. No flukes were detected in the other 11 otters with abnormal gall bladders, possibly as a result of a successful immune response. The majority of otters with thickened gall bladders were in good physical condition but a positive association was not confirmed statistically. Fluke infection was also detected in nine of the 130 otters with apparently normal gall bladders. Liver pathology ranged from mild bile duct hyperplasia and periportal fibrosis to severe sclerosing cholangitis, hepatocyte necrosis and bile stasis. No otters were found to have died as a result of fluke infection, but there was a negative association, approaching significance, between infection and body condition.