Cost-effective strategies to maintain healthy active lifestyle in aging populations are required to address the global burden of age-related diseases. ASPREE will examine whether the potential primary prevention benefits of low dose aspirin outweigh the risks in older healthy individuals. Our primary hypothesis is that daily oral 100. mg enteric-coated aspirin will extend a composite primary endpoint termed 'disability-free life' including onset of dementia, total mortality, or persistent disability in at least one of the Katz Activities of Daily Living in 19,000 healthy participants aged 65. years and above ('US minorities') and 70. years and above (non-'US minorities'). ASPREE is a double-blind, randomized, placebo-controlled trial of oral 100. mg enteric-coated acetyl salicylic acid (ASA) or matching placebo being conducted in Australian and US community settings on individuals free of dementia, disability and cardiovascular disease (CVD) events. Secondary endpoints are all-cause and cause specific mortality, fatal and non-fatal cardiovascular events, fatal and non-fatal cancer (excluding non-melanoma skin cancer), dementia, mild cognitive impairment, depression, physical disability, and clinically significant bleeding. To 20 September 2013 14,383 participants have been recruited. Recruitment and study completion are anticipated in July 2014 and December 2018 respectively. In contrast to other aspirin trials that have largely focused on cardiovascular endpoints, ASPREE has a unique composite primary endpoint to better capture the overall risk and benefit of aspirin to extend healthy independent lifespan in older adults in the US and Australia.