Context: The number of older people living in care homes is increasing. In the UK, this population require greater input from primary care and have a higher admission rate compared to older people living in the community. Older people in care homes experience functional decline over time as well as episodic acute losses in function. Hospital admissions are frequently related to ‘acute functional decline’, which can have many causes. In order to plan research on acute functional decline in the care home population, it is important to understand how this has been described and studied in the existing literature. Objectives: What are the existing working definitions of acute functional decline in older people (aged >65 years)? In what ways has acute functional decline been assessed and/or measured in existing studies of older people? Study Design: Scoping review of the literature. Scoping searches will be carried out to identify papers that address the working definition of acute functional decline (which may include reviews, expert commentary or case reports) as well as studies that have assessed/measured acute functional decline, including (but not limited to) observational studies and trials. Analysis: Narrative review. Expected outcomes: The scoping search should help determine whether it is possible to do a full systematic review of this topic.