The anaesthetist is most commonly involved in the management of patients having computerized tomography (CT) or magnetic resonance imaging (MRI) investigations. There are many articles discussing the relative merits of anaesthesia or sedation for radiological investigations, and many different sedative and anaesthetic techniques have been used. MRI is a rapidly expanding field within radiology and new applications are constantly being found for this imaging modality. All MRI units operate certain patient and personnel exclusions because of the risks of ferromagnetic attraction. Anaesthesia can be maintained with a volatile agent or intravenously. MRI shows much greater detail of the central nervous system than CT. Anaesthesia and monitoring in the MRI suite need to be maintained to the same standards as expected in the operating theatre. The magnetic, RF and gradient fields may cause artefact interference with monitoring devices, especially ECG and pulse oximetry.