Access to medicines is essential for attainment of universal health coverage, which is central to achievement of the health-related Sustainable Development Goals. Controlled medicines include those such as opioids, benzodiazepines, barbiturates, amphetamines and others with identified or emergent clinical indications. WHO recognizes that these medicines are necessary for pre- and post-operative care, for sedation, for the management of both acute and chronic pain, for palliative care, as anticonvulsants (anti-epileptics), for the management of anxiety disorders and for the management of substance use disorders, including as opioid agonist therapy (OAT). The purpose of this guideline is to assist WHO Member States and their partners in developing and implementing balanced national controlled medicines policies to ensure their accessibility, availability and affordability for medical and scientific uses and to minimize the risk of harm arising from non-medical use. The guideline addresses policies for groups (of all ages, from neonates through to older people) affected by conditions in which use of controlled medicines is deemed to be medically appropriate according to evidence-based clinical practice guidelines.