Gnotobiotic pigs were dosed orally with Campylobacter sputorum subspecies mucosalis, either alone, or combined with rotavirus or non-pathogenic Escherichia coli and Streptococcus bovis to study the behaviour of C s mucosalis in defined conditions, to assess intracellular parasitism of enterocytes by C s mucosalis, and if possible to establish an experimental model of porcine intestinal adenomatosis. C s mucosalis colonised the gut of gnotobiotic pigs, persisting for up to 47 days after infection, but did not induce adenomatosis. Despite evidence of limited penetration of the mucosa up to two days after infection, the majority of C s mucosalis remained in the gut lumen. Rotavirus did not enhance invasion of enterocytes by C s mucosalis. The presence of E coli and S bovis caused an increase in the total numbers of C s mucosalis in the gut, but did not affect their distribution. Thus C s mucosalis was largely non-pathogenic in gnotobiotic pigs.