Hydrocephalus is most commonly diagnosed in the first few months of life, though cases also arise in later life. Cerebrospinal fluid shunts used to control the condition are prone to colonization particularly by Staphylococcus epidermidis. The incidence is very much higher in infancy than in older age groups, and this is probably due to prolonged hospital stay as a result of the underlying pathology, combined with the propensity for a high skin bacterial density with more adherent strains, rather than to any immune immaturity. Diagnosis of shunt colonization is often very difficult and serological tests have an important role to play even in infancy. There are several pitfalls in diagnosis, particularly in the elderly. Treatment of shunt infections should include removal of the colonized shunt, though regimens to avoid this are currently being investigated. Intraventricular therapy with vancomycin along with intravenous rifampicin offers the best chances of success at the first attempt. Shunted patients who contract purulent bacterial meningitis should not have their shunts removed but should be treated in the same way as those without shunts.