During a 10-year period shunt infections occurred in 27% of the 289 hydrocephalic patients who had cerebrospinal fluid shunts inserted at Children's Hospital Medical Center. The rate of infection did not vary with the type of shunt. Staphylococcus epidermidis and Staphylococcus aureus were responsible for one-half and one-quarter of the infections, respectively. Removal of the infected shunt in conjunction with administration of systemic antibiotics was effective therapy. Use of systemic antibiotics alone was generally ineffective and was associated with an increased mortality rate. Infection itself was a significant risk factor, raising the mortality rate from 17% to 40%. Clustering of infection within two months of surgery and similar rates of infection for ventriculo-atrial and ventriculo-peritoneal shunts indicate that the infecting organisms are usually introduced during the perioperative period. The possibility that prophylactic antibiotics or different shunt materials might reduce the infection rate requires further study.