An outbreak of proliferative haemorrhagic enteropathy (PHE) occurred in two epidodes and affected 372 adult pigs in the breeding units of a minimal disease piggery; 186 pigs died. In the initial episode breeding sows and boars of all ages were affected, suggesting infection of a fully susceptible population. Animals involved in the first episode of the disease did not show clinical symptoms at a later date and further clinical cases occurred only in animals introduced into the breeding population. Antibiotic feed medication was an effective method of prophylaxis. Bacteria resembling Campylobacter sputorum subspecies mucosalis were isolated from the intestinal mucosa of affected animals.