Rheumatological disorders frequently have gastrointestinal manifestations and, conversely, intestinal disorders frequently have rheumatological manifestations. The possibility of altered intestinal permeability in arthritic patients may provide the bridge needed to link the two organ systems. The normal intestine absorbs nutrients and excludes the remaining material. If the intestine were less discriminating or 'leaky' then material normally excluded would be able to cross the intestinal mucosa into the lamina propria. An inflammatory response to these antigens, be they dietary, bacterial, or viral in origin, could produce either local or systemic disease. This would depend upon the type of immunological response and the cross-reactivity between the host's antigens and the absorbed antigens. This theory could account for the postulated relationship between intestinal abnormalities and the pathogenesis of some forms of arthritis.