The majority of ankylosing spondylitis (AS) patients not only possess HLA-B27, but during active phases of the disease have elevated levels of total serum IgA, suggesting that a microbe from the bowel flora is acting across the gut mucosa. Biochemical studies have revealed that Klebsiella bacteria, not only possess 2 molecules carrying sequences resembling HLA-B27 but increased quantities of such microbes are found in fecal samples obtained from AS patients and such patients have Crohn's like lesions in the ileo-caecal regions of the gut. Furthermore AS patients from 10 different countries have been found to have elevated levels of specific antibodies against Klebsiella bacteria. It has been suggested that these Klebsiella microbes, found in the bowel flora, might be the trigger factors in this disease and therefore reduction in the size of the bowel flora could be of benefit in the treatment of AS patients. Microbes from the bowel flora depend on dietary starch for their growth and therefore a reduction in starch intake might be beneficial in AS patients. A "low starch diet" involving a reduced intake of "bread, potatoes, cakes and pasta" has been devised and tested in healthy control subjects and AS patients. The "low starch diet" leads to a reduction of total serum IgA in both healthy controls as well as patients, and furthermore to a decrease in inflammation and symptoms in the AS patients. The role of a "low starch diet" in the management of AS requires further evaluation.