We have conducted an open pilot trial to assess the therapeutic effect of the lipoxygenase inhibitor, benoxaprofen, in 10 patients with active ulcerative proctocolitis. After 18 days treatment with benoxaprofen (600 mg daily) there was no significant change in bowel habit, rectal bleeding, constitutional upset, sigmoidoscopic appearance, mucosal histology, haemoglobin, ESR, serum albumin or serum orosomucoid. Benoxaprofen itself seems unlikely to prove useful in ulcerative colitis, but evaluation of the therapeutic potential of other lipoxygenase inhibitors in inflammatory bowel disease may be worthwhile.