An increased association of ulcerative colitis and coeliac disease has been reported, as have the results of several small-bowel biopsy studies in ulcerative colitis. Forty-two patients from a population of 438 patients with coeliac disease had rectal biopsies. Fourteen of these showed inflammation of various degrees of severity, including three compatible with a diagnosis of ulcerative colitis. The presenting complaint in 34 of these patients was diarrhoea or steatorrhoea. Twenty-seven patients had coeliac disease diagnosed at the same time or after their rectal biopsy. The other 15 were previously diagnosed coeliacs. Twelve of the 14 patients with abnormal rectal biopsy specimens were known to have subtotal/total villous atrophy at the time of rectal biopsy. Proctitis as seen in these coeliac patients had no unique features to differentiate it from proctitis caused by other disorders. The diarrhoea/steatorrhoea stopped in all patients on commencement of a gluten-free diet, except in those with ulcerative colitis. Proctitis is common in patients with coeliac disease presenting with diarrhoea/steatorrhoea. This study supports the finding of an increased association of coeliac disease and ulcerative colitis and is, to our knowledge, the first rectal biopsy study of a coeliac population.