Monitoring plays an essential role in the management of critically ill children, although continuous observation along with frequent clinical examination remains the best readily available monitor. Unfortunately, human beings do not have the capability of a prolonged, uninterrupted attention span and nurses often have multiple tasks assigned that limit their ability for continuous observation. Furthermore, some information cannot be obtained accurately by clinical examination alone, e.g. oxygen saturation, ICP, etc. Therefore, it is important to understand the principles and practical points to be able to use these monitors, and first rule out malfunction, disconnection, or improper electrode placement when abnormal reading appear on these monitors before initiating clinical intervention on a patient.