Background and aims Unlicensed and off label drug use in children is common and leads to well-recognised problems. This study aimed to determine whether a relationship exists between medication errors and licence status.

Methods Reports of errors in a UK children's hospital from 2004 to 2006 were analysed in terms of licence status and degree of harm and compared to the incidence of unlicensed and off label drug use in the hospital.

Results 20 of 158 (13%) errors were considered to have caused moderate harm and 12 of these involved unlicensed/off label drugs. 138 (87%) caused no or low harm. None caused severe harm. Unlicensed drug usage was significantly more likely to be associated with errors than licensed use in both children and neonates.

Conclusion Unlicensed drug use appears to be associated with medication errors in neonates and children. Medication errors causing moderate harm were significantly more likely to be associated with both unlicensed and off label than licensed drugs.