Spirochaetes are well known causative agents of diarrhoea in veterinary medicine. In human medicine the relationship between presence of spirochaetes in the colon on the one hand, and its clinical significance on the other, is far less clear. In the majority of cases the colonization of the colon with these micro-organisms seems to represent a commensal relationship with the host, and is almost always a coincidental finding with no association with the clinical symptoms of the patient whatsoever. Very infrequently the organism may become invasive. In this article the literature on human intestinal spirochaetosis is reviewed, and key points for daily clinical practice are emphasized.