The abdominal intraperitoneal cerebrospinal fluid pseudocyst is an infrequent but important complication in patients with ventriculoperitoneal shunts. Since 1954, 115 cases of paediatric pseudocysts have been reported in the literature. One additional report deals with an adult patient. We report on 14 cases of sonographically diagnosed abdominal pseudocysts. Their aetiology, diagnosis, clinical signs and symptoms and surgical management are investigated. In our hydrocephalus series we have an incidence of pseudocyst formation of 4.5%. The most common presentation of the paediatric patients is with symptoms of elevated intracranial pressure and abdominal pain, whereas the adults have predominantly local abdominal signs. Diagnosis is readily made with ultrasonography. Predisposing factors for pseudocyst formation are multiple shunt revisions and infection. Microscopically, the pseudocysts consist of fibrous tissue without epithelial lining. The treatment involves surgical removal of the catheter with or without excision of the pseudocyst wall and placement of a new catheter intraperitoneally in a different quadrant or an intra-atrial shunt. Recurrences are rare, especially under appropriate medical treatment of infection. In our series, microbiologically proven infection was present in 30% of the cases.