We report 7 cases of sigmoid colon infection in patients taking TNFα antagonist therapy to treat chronic inflammatory joint disease. There were 5 women and 2 men with a mean age of 57.5years (range, 21–77years). The presenting symptoms were abdominal pain, bowel habit changes, and a fever. These symptoms developed within 6months after starting TNFα antagonist therapy in 5 of the 7 patients. Empirical antibiotic therapy was used in all 7 patients. Surgical colectomy was performed in 4 patients, including 1 who required a temporary Hartmann's procedure. The risk of infection associated with TNFα antagonist therapy is well documented. However, few cases of colon infection have been reported and little is known about this potentially severe complication. Glucocorticoids or non-steroidal anti-inflammatory drugs may worsen the infection, particularly as they can attenuate the clinical symptoms, thereby delaying the diagnosis. A history of sigmoid colon infection, diverticulosis, and/or diverticulitis must be sought before starting treatment with a biological agent. Prophylactic treatment may be considered if such a history is found. Diagnostic investigations are in order to develop a standardized management strategy in patients with a history of intestinal tract infection.