It has been proposed that the reduction inn-butyrate oxidation by colonic epithelial cellsobserved in ulcerative colitis may be related toexposure to reduced forms of sulfur derived fromdissimilatory sulfate reduction by luminal microflora. Thisstudy aims to compare stool sulfide concentrations incontrol and colitic subjects. Control subjects hadsignificant colorectal disease excluded by virtue of their selection. Patients with ulcerativecolitis were stratified by disease extent and activity,and by salicylate drug use. Stool sulfide was measuredusing a direct spectrophotometric method on NaOH (free sulfide) and zinc acetate (total sulfide)stool slurries. Fifteen control and 19 colitic subjectswere studied. There was no significant difference instool sulfide between control and colitic patients (free sulfide, control =0.52 (0.17), colitic0.45 (0.10), t = 0.36, P = 0.71, total sulfide, control1.33 (0.21), colitic 0.96 (0.15), t = 1.44, P = 0.16).Disease extent or activity did not significantlyinfluence stool sulfide. These results do not support aprimary etiologic role for luminal sulfide in ulcerativecolitis.