Medication use is the most common health-related action taken by Australians and, if used correctly, can significantly improve health outcomes. However, there are also potential harms and negative consequences related to medicines use. Rational prescribing (RP) is the judicious, appropriate, safe and efficacious use of medicines, and is known to be a challenging area for GP registrars. GP supervisors play a key role in influencing GP registrar prescribing. This tutorial is linked to the supervision activity of prescribing audit and feedback.