An analysis of 160 patients with Reiter's disease, 144 with yersinia arthritis, and 9 with salmonella arthritis was performed, Complete or incomplete Reiter's syndrome was observed in one-third of the patients with yersinia arthritis and in most of those with salmonella arthritis. During the followup period, chronic back pain and joint symptoms were frequent in all the patient groups. Patients who were HLA-B27 positive had a more severe acute disease (more frequent back pain, urologic symptoms, mucocutaneous manifestations, and a longer duration of the disease) and more frequent chronic back pain and sacroiliitis.