This chapter describes a theatre intervention that uses professional acting instruction to lower risk factors for Alzheimer’s disease and other forms of dementia. Please note that this is not a form of drama therapy, which treats those already afflicted, but is a preventive programme designed to help older adults remain cognitively healthy. The intervention has been supported by four multi-year grants from the National Institutes of Health as well as a number of private funders. The rationale behind this programme is that the practice of acting offers intense mental stimulation because it requires participants to retain theatrical dialogue verbatim without deliberate memorisation, and to perform dramatic scenes truthfully in front of an audience of their peers. This latter aspect of acting has been variously referred to as the ‘reality of doing,’ ‘being in the moment’ and ‘living truthfully under imaginary circumstances,’ and is a process that lies at the heart of professional acting. This chapter presents evidence that this approach to performance confers unique cognitive benefits to older non-actors, including increases in episodic memory, list recall, creativity and problem-solving ability, as measured by reliable and valid scientific assessment instruments. The programme has been carried out successfully for over 20 years in dozens of independent-living retirement homes and community senior centres in the USA.