59 outpatients with irritable bowel syndrome participated in a randomised double-blind trial. The patients in the treatment group received three biscuits daily each containing 10 g of ordinary miller's bran, whereas the patients in the control group received wheat biscuits of a similar appearance. The treatment period was 6 weeks. 52% of the patients in the treatment group noted subjective improvement compared with 65% in the control group. The results of this trial do not support the routine use of miller's bran in irritable bowel syndrome.