Campylobacter mucosalis and C hyointestinalis have been associated with the proliferative enteropathies of pigs. An examination of the antibody response to these organisms and to the intracellular campylobacter-like organism was undertaken. Antibody to the campylobacter-like organism was predominantly IgM, short lived, and could be detected by an immunofluorescence test using bacteria released from lesions as antigen. The majority (75 per cent) of pigs with proliferative enteropathy at necropsy were antibody positive and a small number (4 per cent) of pigs in which lesions were not observed were found to have antibody. Antibody appeared to be correlated with the presence of lesions rather than with exposure to infection and was independent of the presence of antibody to C mucosalis or C hyointestinalis. In natural outbreaks of the disease antibody to the campylobacter-like organism was more prevalent than clinical signs in the affected animals.