Rheumatic manifestations due to Yersinia pseudotuberculosis are apparently rare. We report four personal observations, including one of a patient with Reiter disease and significant titres of antibodies to Yersinia pseudotuberculosis. In all four patients a non-specific syndrome, with fever and digestive symptoms, preceded the onset of joint disease. Both peripheral and axial joints were affected. One patient had HLA B27; the brother of another patient had spondyloarthropathy with HLA B27. Stool cultures were negative but they were all done at least three months after the acute episode. These rheumatic manifestations have many features in common with those described in Yersinia enterocolitica infections. Studies of larger series could improve our knowledge of the part played by the patients' constitution and widen the scope of reactive arthritis.