PURPOSE OF REVIEW: Despite the prevalence of Campylobacter jejuni and the importance of the disease, investigations into pathogenesis have been restricted because of the absence of a convenient animal model of disease. In particular it is still unclear how C. jejuni infection causes diarrhoea. RECENT FINDINGS: Recent developments in improved models of infection and studies on the innate immune responses have provided a deeper understanding of host-pathogen interactions. From the organism's perspective, further genomics-based information including two new genome sequences has provided much basic information, particularly relating to cell surface glycostructures. SUMMARY: Research over the last few years is starting to address the gaps in our knowledge of how this important human pathogen interacts with host cells and causes diarrhoeal disease. Further research is required for a detailed understanding of these interactions and also to develop intervention strategies to reduce the burden of C. jejuni-associated disease.