In cattle, bracken fern chronic toxicity is characterized by the presence of multiple tumours in the bladder (bovine enzootic haematuria). From October 1999 to March 2003, 433 urinary bladders with macroscopical lesions were collected in the slaughterhouse of São Miguel Island (Azores, Portugal), an endemic area where Pteridium aquilinum infestation in pastures is high. Bladder lesions were divided into three main categories (inflammatory lesions, non-neoplastic epithelial abnormalities and tumours) and described in detail. In some cases, neoplastic growth was confined to a single site, but in most cases multiple tumours developed within the same bladder. Epithelial tumours alone were present in 51.2% of the affected bladders, mesenchymal tumours alone in 17.4%, and both epithelial and mesenchymal tumours in the remaining 31.4%. The large number of tumours examined (870) revealed new categories not yet included in other veterinary classification systems, namely, inverted papilloma, papillary neoplasm of apparent low malignant potential, and haemangioendothelioma.