Twenty-four patients were under observation. It is shown that reactive arthritides requiring surgical treatment are often of Yersinia etiology. A preceding episode of acute diarrhea can be revealed in the immediate anamnesis. Besides affection of the joints, the clinical picture is characterized by protracted high fever, general toxicosis syndrome, enlarged mesenteric lymph nodes, and, occasionally, enlargement of the liver and spleen. The diagnosis is confirmed by identification of specific antibodies in blood serum. Yersinia arthritides are unresponsive to the routine therapy. Administration of chloramphenicol and/or gentamicin with indomethacin produces a rapid positive effect.