Respiratory disease is ubiquitous in hospitals and community healthcare settings in the UK. Nurses, therefore, must be able to understand the physiology and pathophysiology that underpins the care they provide for people living with a respiratory disorder. This article summarises the fundamental anatomy and physiology of the respiratory system and respiration. It also explores the pathophysiological changes that occur in the four most common respiratory conditions, namely pneumonia, lung cancer, asthma and chronic obstructive pulmonary disease. Key elements of a comprehensive respiratory assessment and how nurses can determine acute deterioration are explored. The case study and reflective questions aim to enhance the reader's understanding of respiratory assessment and nursing care.