AbstractBackgroundNICOLA, the largest public health cohort study of ageing in Northern Ireland, commenced in 2013 with a representative sample of ∼8500 individuals aged 50 years and over living across Northern Ireland.HCAP is a National Institute on Ageing (NIA) funded sub‐study designed to assess prevalence of cognitive impairment and dementia in a sample of 1000 participants aged 65 years and older.A dress rehearsal was carried out prior to the main study to implement the study as per the HCAP study protocol. This, ensured any issues could be identified prior to the main phase and the Standard Operating Procedures (SOP) could be amended accordingly.Method14 participant interviews and 14 informant interviews were completed between December 2021 and January 2022.The HCAP dress rehearsal sample was selected from the NICOLA research advisory panel, which included NICOLA participants and individuals from the charity group AgeNI.The study consisted of a face‐to‐face participant interview, comprising nineteen different measures of memory and thinking.During the informant interview a family member or friend was asked about participant’s ability to perform daily tasks and their social and cognitive activities.During the HCAP dress rehearsal, fieldwork staff conducted home visits in pairs: one conducting the interview while the other observed. Staff completed feedback forms which provided opportunities to comment on the use of computer software, consent processes and the administration of memory and thinking assessments.ResultSeveral areas for improvement were highlighted:Pre‐Visit Documentation: Fieldwork staff reflected on the complexities of test administration and the transition between computer and paper assessments. Pre‐visit protocols were revised to include preparation processes.Test Administration: Queries were raised on the logistics of test administration and scoring. These were resolved through contact with the Health and Retirement Study (HRS) team.Study Administration Processes: Additional administration databases were created and SOPs amended to ease the flow of recruitment and home visit bookings.ConclusionThe HCAP dress rehearsal highlighted the importance of pre‐visit preparation and staff training, combined with clear procedures and protocols to allow for the collection of high quality data and enhancement of the study experience for participants and researchers.