Infection remains a major cause of morbidity and mortality following CSF shunt procedures. In this study 191 shunt procedures carried out from January 1981 to December 1992 in a series of 81 infants (less than 6 months old) were retrospectively analyzed for possible risk factors. The overall surgical infection rate was 7.8%, with 15 infections occurring in 14 patients (17.2%). No significant difference in the rate of infections was found in relation to sex, birth weight, gestational age, and type of shunt procedure (primary insertion/revision). The occurrence of other infections during the period of shunt surgery did not influence the infection risk either. Intraventricular hemorrhage and central nervous system infections as causes of the hydrocephalus were found to correlate with septic risk. Young age (less than 6 months) seems to represent the main risk factor, and this is related both to the immunologic deficiency and to the particular features of residential bacterial flora in this age group.