The intestinal tracts of 363 horses were examined after slaughter at a horse abattoir. The presence or absence of Anoplocephala perfoliata and the sites of attachment were recorded. A total of 51 per cent of the horses had A perfoliata attached to the mucosa of the ileocaecal junction and/or to the caecal mucosa; 5 per cent of the horses had A perfoliata attached only to the mucosa of the ileocaecal junction, 24 per cent had A perfoliata attached only to the caecal mucosa and 22 per cent of the horses had A perfoliata attached at both sites. The degree of infestation did not appear to be influenced by the season or by the age, breed or source of origin of the horses. The lesions at the sites of attachment included congestion, oedema, ulceration, diphtheresis, mucosal thickening, eosinophil infiltration and fibroplasia. The severity of the lesions was exacerbated by increasing numbers of worms.