Presence of antineutrophil cytoplasmic auto-antibodies (ANCA) in ulcerative colitis could be an epiphenomenon related to colonic inflammation and/or may reflect a primitive disturbance of immune regulation. In this regard, study of ANCA status after the whole colorectal mucosa has been removed could favor one of these two hypothesis. We compared the prevalence of ANCA in a first group of 70 patients with non operated UC and in a second group of 32 patients with UC having had a proctocolectomy with ileoanal anastomosis. Perinuclear ANCA (p-ANCA) were found in 34/70 (49%) of the first group as compared to 11/32 (34%) in the second group (NS). Our results further support that the presence of ANCA in UC reflects an immune disturbance not linked to the presence of the target organ.