Mucocele of the appendix is an uncommon disorder, characterized by a cystic dilatation of the lumen. It is often diagnosed clinically from signs and symptoms of acute appendicitis or, if it is asymptomatic, as an incidental finding during ultrasonography, computed tomography, and radiographic examinations of the gastrointestinal tract, or laparotomy. The incidence of mucocele ranges from 0.2% to 0.3% of all appendectomy specimens. We report five cases of appendiceal mucocele (all women, aged 19-90 years), who were admitted from January 1993 to January 2003 to our hospital. These cases represent 0.29% of the 1720 appendectomies performed during this period. Three of the patients were symptomatic and had appendectomies. The final diagnosis for mucocele was given at laparotomy. No colon neoplasms were identified during surgery, and subsequent colonoscopic examinations were also negative. The other two patients were asymptomatic of appendiceal tumor. Colonoscopy revealed two colonic malignant tumors in one patient and an adenocarcinoma of the sigmoid colon in the other. Mucocele of the appendix was diagnosed pre-operatively by ultrasound and computed tomography. One of the two patients underwent a right hemicolectomy and sigmoidectomy; the other one underwent an appendectomy, cecostomy and sigmoidectomy. Four of the patients recovered and are doing well today; one patient died on the twenty-fifth postoperative day. The most common symptom of mucocele is abdominal pain, although many patients may be asymptomatic. Mucocele is often associated with concomitant colon cancer, thus patients with this tumor should be systematically checked for other colonic lesions.