Purpose -This paper describes a service improvement project with two aims: to identify and screen all adults with Down's syndrome aged over 30 years in a defined locality using a standardised instrument to establish functional baselines; and to set up a database to facilitate early diagnosis of dementia in this population.Design/methodology/approach -An assistant psychologist used a standardised instrument to screen participants who were identified through contact with health, social, and third sector, and housing services.Findings -Eligible people were identified and screened using an informant-based measure. Three groups were identified: group 1 showed no significant change; group 2 showed significant change but no signs of dementia; and group 3 showed significant change plus signs of dementia. People with suspected dementia were referred on for further investigation/assessment and supportive services.Practical implications -Terminology is important in engaging families in a screening project, as is the opportunity to provide information. A proactive screening project can be established by employing working partnerships between intellectual disability and older adult services to aid diagnosis.Originality/value -Adults with Down's syndrome aged over 30 years in a defined locality can be identified through contact with health, social, and third sector, and housing services. Those identified can be screened using a standardised instrument and a database of screening results established in order to establish baselines against which future re-screening can be conducted. Partnership working between older adult mental health services and intellectual disability services can improve the diagnostic service to adults with Down's syndrome.