BACKGROUND: Mucoceles of the appendix are rare. After appendectomy, mucoceles are detected with a frequency of 0.2 to 0.3 %. Both stenosing / obliterating processes and alterations of the epithelium (hyperplasia, mucinous cystadenoma, cystadenoma with uncertain malignant potential (UMP), mucinous cystadenocarcinoma lead to the occurrence of mucoceles. The perforation of a mucocele with possible spread of mucus and cells into the abdominal cavity constitutes a severe complication (pseudomyxoma peritonei). Surgical resection is the curative approach for mucoceles of the appendix. MATERIALS AND METHODS: Data of patients who were treated for an appendiceal mucocele between 1995 and 2009 were analysed retrospectively with regard to clinical presentation, diagnostic measures, surgical procedure and histopathological result. Follow-up was evaluated in telephone interviews. RESULTS: We extracted 5 cases from our database. Clinical symptoms varied greatly among the individual patients, ranging from peracute abdominal pain in the right lower quadrant to chronic obstipation. Results from abdominal ultrasound and / or abdominal CT scans contributed to the indication for surgical intervention in all cases. In 2 patients surgery was stated as urgent whereas in 3 the operation was scheduled electively. In one patient the diagnosis of an appendiceal mucocele was stated preoperatively and in another intraoperatively. In 3 patients only the histopathological result revealed the underlying mucocele. We performed 1 open and 1 laparoscopic appendectomy, 1 open appendectomy with a partial resection of the coecum and 2 laparoscopic ileocoecal resections. One of the patients had a pseudomyxoma peritonei. The histopathological diagnoses ranged from mere epithelial hyperplasia to an adenoma with uncertain malignant potential and a mucinous cystadenocarcinoma. One patient's long-term follow-up could not be evaluated. All other patients had neither recurrence nor any complications after discharge. CONCLUSIONS: Mucoceles of the appendix present with a wide spectrum of clinical symptoms and histopathological alterations. Only an accurate histological analysis reveals the underlying pathological lesion correctly. This study emphasises that a mucocele of the appendix constitutes an important differential diagnosis in patients presenting with pathologies in their right lower abdominal quadrant.