Appendectomy is associated with a reduced risk of developing ulcerative colitis (UC). In addition, there may be appendicular involvement in UC in patients with extensive or even left-sided disease. However, no data are available on the incidence, clinical presentation and outcome of acute appendicitis in patients previously diagnosed with UC. The impact of appendectomy in this subset of patients also remains to be determined. We describe 2 cases of acute appendicitis in the setting of inactive extensive ulcerative colitis and compare their histologic features with those of the surgical specimens of 2 further UC patients colectomized for refractory and extensive disease.