A group of 205 patients (115 children and 90 adults) with a total of 212 intracranial pressure (ICP) monitors were retrospectively studied with attention to daily cerebrospinal fluid cultures, duration of monitoring, associated cranial injuries, and hospital site of the ICP monitor (intensive care unit or operating room). Only closed ICP monitoring systems without irrigation or compliance testing were used, and all patients received antibiotics as prophylaxis throughout the monitoring period. There were no complications associated with monitor placement. Incidence histograms and regression analysis were used to determine the daily risk of subsequent infections, in addition to evaluating the cumulative risk of infection, as has been previously described in the literature. No relation between the duration of ICP monitoring and the rate of daily infection through the period of maximal monitoring (1-2 weeks) was found in this series. The overall incidence of infection was 7.1% with a median duration of monitoring of 7.2 days. The age of the patient (adult vs. child), site of ICP monitor placement, and nature of the underlying disease (trauma vs. nontrauma) had no significant effect on the development of monitor-related infections in our study. These data indicate that the decision to continue ICP monitoring can be based solely on the clinical necessity for further monitoring rather than on concerns for monitor removal to prevent infection.