The ultrastructure of the livers of four-week-old White Rock broiler chickens fed diets containing 50% rapeseed meal was examined. Multifocal hepatocytic necrosis was observed in most of the birds fed the experimental diets. Early degenerative changes were swelling of mitochondria and vacuolations of various sizes in the cytoplasm of the hepatocytes. The reticulum fibres seen as bundles of cross striated fibrils were disorganised at the sites of the focal necrosis. Alteration of interfibrillar matrix were considered to be reason for the negative silver stain in the necrotic foci at light microscopic level reported previously. Disruption of the liver framework at the necrotic foci appeared to have caused a rupture of the sinusoids in the birds showing the haemorrhagic syndrome.