Drug prescribing is a multifaceted and technically complex process requiring careful judgement of the competing risks of harm and benefits of treatment. Good prescribing requires knowledge of your patient’s illness, comorbidities, and concurrent treatments. When prescribing, a doctor must be aware of a drug’s potential for toxicity, its metabolic or excretory pathway, its interactions, its cautions and contraindications, and its legal status. Since the enactment of the UK Human Medicines Regulations 2012, prescribing of medicines may be undertaken by any suitably qualified doctor, dentist, and various other groups recently given prescribing privileges. All groups have a duty to prescribe medicines within their area of competence and scope of practice, as failure to prescribe medicines safely is responsible for a significant amount of reported serious medication incidents. This chapter will review the law concerning prescribing, the liability imposed on suppliers, consent issues, non-standard prescribing, and the legal status of non-allopathic medicines.