Critically ill patients are at high risk for the development of delirium and agitation, resulting in non-compliance with life-saving treatment. The use of physical restraint appears to be a useful and simple solution to prevent this treatment interference. In reality, restraint is a complex topic, encompassing physical, psychological, legal and ethical issues. This article briefly discusses the incidence of delirium and agitation in critically ill patients and examines in detail the method of physical restraint to manage treatment interference. The historical background of physical restraint is discussed and the prevalence of its use in critical care units across the world examined. Studies into the use of physical restraint are analysed, and in particular the physical effects on patients discussed. The use of physical restraint raises many legal, ethical and moral questions for all health care professionals; therefore, this study aims to address these questions. This article concludes by emphasizing areas of future practice development in intensive care units throughout the UK.