The intrathecal infusion test leads to a more accurate diagnosis of communicating hydrocephalus, and is useful in identifying those patients with insufficient cerebrospinal fluid (CSF) absorption who are most likely to improve after a shunt operation. Furthermore, shunt function can be evaluated by assessing the CSF absorption of shunt-operated patients in the same way. Some patients do not improve after surgery because of irreversible or shunt-independent neurological and radiological signs, while the postoperative infusion test demonstrates a normal shunt function. The clinical condition and neuroradiological picture of such patients cannot be improved by shunt revision if the implanted shunt already allows a normal CSF outflow. By means of infusion tests the number of patients who need a further operation can be reduced, with a consequent drop in shunt infections, a very welcome aspect especially in pediatric neurosurgery. In our department 298 infusion tests were carried out over a seven-year period, and a decrease in shunt revisions and infections could be observed.