Arthritis following certain Salmonella infections, dysentery, and nonspecific enterocolitis exemplifies the fact that intestinal infections can elicit rheumatic reactions. Recent observations indicate that in the last mentioned group specific microbes, such as Clostridium perfringens and Yersinia enterocolitica, may be involved. References are made to the findings of an abnormal intestinal flora, notably C. perfringens, in patients with chronic arthritis and of circulating and cell-bound antibodies to C. perfringens alphatoxin as evidence of an immunologic response to this microbe in rheumatoid disease.