The indications for sedation in the paediatric intensive care unit (PICU) patient are varied ranging from short term use for various procedures to prolonged administration to provide comfort during mechanical ventilation. When faced with the decision to institute sedation, the healthcare provider must make three decisions: the agent to be used, the route of delivery, and the mode of administration (intermittent versus continuous). There are several agents that have been used to provide sedation in the PICU patient including the inhalational anaesthetic agents, benzodiazepines, opioids, ketamine, propofol, chloral hydrate, phenothiazines, and the barbiturates. This review describes the various agents for sedation and discusses their advantages and disadvantages as they pertain to the PICU. Consequences of and treatment strategies for long term problems with prolonged sedation including tolerance, physical dependency, and withdrawal are reviewed.