Quality assurance has its roots in industry and therefore is strongly influenced by concepts from business, hence the reference to the definition of the term ‘quality’ according to the International Standard Organization (ISO), for example. In order to better understand the various concepts of quality assurance, this chapter clarifies concepts such as ‘effectiveness’, ‘efficiency’, ‘patient-centredness’, and ‘equity’. Of major importance in clinical medicine are guidelines, standards, recommendations, and their grade of evidence. Guidelines in particular have the advantage of facilitation of the practice of evidence-based medicine in that they can provide a practically orientated summary of the relevant research literature. Other important tools for quality assurance include ‘plan–do–study–act’ (PDSA) cycles, process mapping, monitoring of outcome indicators, auditing, and peer review. Patient safety is another rather young discipline in academic medicine. Triggered by the landmark publication of To Err is Human by the US Institute of Medicine (IOM) in 1999, patient safety gained widespread attention in healthcare. Anaesthesiology as a typical safety discipline was among the first to adopt safety measures such as ‘incident reporting’ or ‘human factors training’ years before the IOM report. Safety is closely related to outcome and therefore mortality, morbidity, as well as adverse events in general have to be considered. In order to improve, safety lessons can be learned from the so-called high-reliability organizations and transferred into clinical practice.