SummaryChildren undergoing computerized tomography (CT) or magnetic resonance imaging (MRI) need to be motionless for optimal image quality and therefore often need sedation or anaesthesia. Intravenous thiopentone alone has not been described for such procedures in children. The authors evaluated intravenous thiopentone as a sole anaesthetic for CT/MRI in 200 unpremedicated children mean age 2.9 ± 2.5 years (range 1 month‐12 years). An initial dose of thiopentone 6 mg·kg−1was given to all children; incremental thiopentone 1–4 mg·kg−1was administered at the anaesthetist's discretion. A single dose of thiopentone 6 mg·kg−1was sufficient to complete the scan in 30% of children. The mean total thiopentone dose was 8.5 ± 3 mg·kg−1. The mean duration of CT/MRI was 40 ± 21 min. Tracheal intubation was necessary in 2 children (1%); both had coughing episodes that precluded adequate imaging. Eighty‐three percent of children were awake within 5 min of completing the scan and did not require recovery room admission. A single episode of vomiting occurred post‐operatively in 7% of children. Intravenous thiopentone is a simple, reliable method of providing sedation/anaesthesia to children undergoing radiologic procedures. Tracheal intubation or use of other forms of airway support is rarely necessa