This chapter begins with an explanation of the causes of infection and then focuses on healthcare‐associated infections (HCAIs), specifically describing the steps to be taken to minimize the risk of individuals acquiring infections while receiving healthcare. The chapter gives an overview of key principles, terminology and definitions, and describes the standard precautions that must be taken with patients at all times regardless of their known infection status. It also covers additional precautions that may be required because the patient is colonized or infected with micro‐organisms that may pose a particular risk to others, or because they are particularly vulnerable to infection themselves. The chapter additionally describes the specific precautions that must be taken during invasive procedures, in particular aseptic technique.