The cerebrospinal fluid shunt operation, from its first realization in 1908 by Kausch till our days, is still of a significant importance for the long-term treatment of the internal hydrocephalus. Well known are many complications connected with the use of the valve systems (malfunction, infectious, overdrainage, secondary craniosynostosis and etc.). For a period of 17 years (1984-2000) at the Clinic of Pediatric Neurosurgery, Department of Neurosurgery, Sofia Medical University, 414 cerebrospinal fluid shunt operations were performed on children. 216 were drained to the right atrium of the heart, 198 to the peritoneal cavity. They were followed up by catamnesis until the year 2001. The authors describe 2 extremely rare cases with post-shunt complication as a result of a malfunction of the valve system, owing to a migration of the distal catheter: 1) in the anus; 2) in the urethra. In the first case the distal catheter perforated the colon transversum and by the way of the intestines went out through the anus. In the second case the distal catheter protruded out of the body through the bladder and the urethra. Their clinical appearance, the diagnostic examinations and the operative treatment are shown.