93 patients with rheumatoid arthritis (RA) were examined for histological or other evidence of gut abnormalities. 44 had raised levels of IgG to gliadin, and of these 38 (86%) were also positive for IgA rheumatoid factor (RF). 24 patients (15 with raised levels of IgA RF and wheat protein IgG [AB+] and 9 with normal levels of both antibodies [AB-]) underwent jejunal biopsy. 6 of the AB+ and 1 of the AB- patients had villous atrophy. The AB+ group had lower villous surface/volume ratio and small intestinal lactase concentrations than did the AB- group or age-matched controls. There was no significant difference between the two groups of RA patients in disease severity or treatment regimen. The findings suggest that the gut may play a more important part in the immunopathogenesis of some cases of RA than in others, and that the former may be identified by raised levels of IgA RF and wheat protein IgG.