The University of Melbourne has appealed to Victorians to join the world's largest drug trial which aims to delay the onset of Alzheimer's disease.

More than 400 healthy adults aged 65 to 85, who do not have any memory problems, are needed for the Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease study (the A4 study).

Study participants will undergo a simple, painless brain scan.

Researchers from the University of Melbourne and the Florey Institute of Neuroscience and Mental Health will examine the scans for a build-up of amyloid plaques, which can lead to Alzheimer's disease in some cases.

Eligible participants who show high levels of amyloid will either receive a monthly dose of a promising new anti-amyloid drug, or a placebo. Volunteers with low levels of amyloid may take part in a separate observational study.

The study, which has been recruiting since 2015, has recently received a funding boost, thanks to a major donation from the Yulgibar Foundation.

Recruitment will close at the end of 2016 and first results are expected in 2020.

To find out more, or to enrol in the study, visit the The Florey Institute of Neuroscience and Mental Health's website.