Reactive spondylarthropathies include mono- or asymmetrical polyarthritis as well as axial skeletal involvement. Usually they occur after urogenital or gastrointestinal infections caused by Yersinia, Salmonella, Shigella or Campylobacter. Reactive arthritis can also result from infections with other agents. We report the case of a patient with clinical features of seronegative spondylarthropathy. The endoscopic examination revealed intestinal spirochetosis. Other possible arthritogenous agents were ruled out serologically. The pathogenicity of intestinal spirochetosis is controversial. It can be associated with diarrhea. In Western countries the prevalence of intestinal spirochetosis is below 2%, male homosexuals being especially prone to these infections. Spirochetosis is often associated with a mild inflammatory reaction only, while a local increase in IgE plasma cell count has been described.