Ventriculostomies and external ventricular drainage devices are common in neurosurgical and neurocritical care practice. The potential for infection of this low-flow system is significant and the consequences can be severe. Ventriculostomy catheters are commonly used to allow invasive monitoring of elevated intracranial pressure (ICP) secondary to acute hydrocephalus in various neurosurgical disorders such as severe head trauma, subarachnoid hemorrhage, intracranial hypertension, or intraventricular hemorrhage. The primary aim of these catheters is to detect elevated ICP and thereby guide medical or surgical therapies to maintain an adequate cerebral perfusion pressure. The risk factors for catheter-related ventriculitis can be categorized into three groups: (1) patient characteristics and the underlying mechanism of injury, (2) events that break the integrity of a closed system, and (3) environmental influences. Assessment of risk factors is crucial to determine changes in microbial infection and to identify ways to prevent future complications.