Specially processed cereals (SPC) can increase antisecretory factor (AF) activity in humans with an intact intestine. The aim of the present study was to investigate whether AF synthesis could be induced in patients who had been subjected to intestinal resections. Eight patients with varying extents of intestinal resections due to Crohn's disease and six healthy controls participated. All subjects received 54 g SPC daily for 2 weeks. Plasma AF activity was determined before, during and after the treatment period. Baseline diet and medications were kept unchanged. The patients registered the daily number of bowel movements. The SPC diet increased AF activity in all controls. In the patients there was a significant correlation between the length of the remaining small intestine and AF induction (r=0.94, p<0.01) and only those patients with a remaining small intestine of about 3 m reached AF values comparable to those in healthy subjects. It is concluded that small bowel length is related to the ability of humans to induce AF activity by dietary means.