Prescribing by nurses and midwives continues to expand and has consistently been evaluated as safe and effective. This article is part one of two exploring the core professional, legal and ethical dimensions of prescribing. Reference is made to a contemporary prescribing model, RAPID-CASE, devised by the authors to demonstrate the application of key prescribing practice principles. The importance of a structured approach is demonstrated with reference to the Royal Pharmaceutical Society competency framework for all prescribers, applicable legislation and underpinning ethical principles. This first article identifies the main professional dimensions of prescribing practice, while the second article focuses on the legal and ethical aspects.