PURPOSE: Perinuclear antineutrophil cytoplasmic autoantibody is known to be a marker for ulcerative colitis, and anti-Saccharomyces cerevisiae Mannan antibody is a serologic marker associated with Crohns disease. The aim of this study was to assess the value of detecting perinuclear antineutrophil cytoplasmic autoantibody and/or anti-Saccharomyces cerevisiae Mannan antibody for the diagnosis of ulcerative colitis, Crohns disease, Behçets colitis, and tuberculous colitis. METHODS: Serum samples were obtained from 85 patients with Crohns disease, 77 with ulcerative colitis, 36 with Behçets colitis, 14 with tuberculous colitis, 20 healthy controls, and 21 first-degree relatives of patients with Crohns disease. Determination of perinuclear antineutrophil cytoplasmic autoantibody and anti-Saccharomyces cerevisiae Mannan antibody was performed with the standardized indirect immunofluorescence technique and an enzyme-linked immunosorbent assay, respectively. RESULTS: A relatively high percentage of patients with Crohns disease (49.4 percent), relatives of Crohns disease patients (61.9 percent), and patients with Behçets disease (41.7 percent) tested seropositive for anti-Saccharomyces cerevisiae Mannan antibody compared with normal controls (10 percent). In cases of ulcerative colitis, 44.2 percent tested seropositive for perinuclear antineutrophil cytoplasmic autoantibody, whereas the controls showed 0 percent positivity. The combination of a positive anti-Saccharomyces cerevisiae Mannan antibody test and a negative perinuclear antineutrophil cytoplasmic autoantibody yielded a sensitivity and specificity of 48.2 and 87 percent, respectively, for Crohns disease. The combination of a positive perinuclear antineutrophil cytoplasmic autoantibody test and a negative anti-Saccharomyces cerevisiae Mannan antibody test yielded a sensitivity and specificity of 36.4 and 97.6 percent, respectively, for ulcerative colitis. CONCLUSION: Anti-Saccharomyces cerevisiae Mannan antibody may be associated with Crohns disease and Behçets disease and perinuclear antineutrophil cytoplasmic autoantibody with ulcerative colitis. A combination of both tests may aid the differential diagnosis of inflammatory bowel disease.