To establish patterns of mucin staining in the colon, a differential staining method was developed separating acid mucins into sialomucins and sulfomucins, and their distribution was studied along the colon of 9 normal subjects, 6 patients with ulcerative colitis in remission and 9 with colon cancer. Serial mucosal biopsies from the cecum to the rectum, were taken at colonoscopy and stained with aldehyde-fuchsin and alcian blue. The mean score of staining intensity in normals for sialomucins was higher than for sulfomucins, 1.85 ± 0.05 versus 0.60 ± 0.08 (p < 0.05). A significantly lower staining score for sulfomucins was found in the descending colon and in the cecum when compared with the rectum. Ninety-seven percent of the slides were positive for sialomucins, but only 50% for sulfomucins (p < 0.05). The mean ( ± SE) staining intensity for sialomucins in the ulcerative colitis and cancer groups was 1.60 ± 0.08 and 1.60 ± 0.05 (p = 0.002 and p < 0.05 when compared with the controls, respectively). A difference in the percentage of biopsies positive for sulfomucins, in controls and proctosigmoiditis groups, was also observed: 50.0 and 33.3%, respectively (p = 0.013). No significant change was demonstrated in the mean sulfomucin staining score comparing normal and colon cancer patients. Our results may be used as a baseline for further research on mucin staining patterns in colorectal inflammatory and neoplastic dise