OBJECTIVES: The objective of this study is to quantify the strength of preferences of older Americans for possible Alzheimer's disease (AD) treatment benefits by estimating their willingness to accept the risk of death or severe disability in exchange for modifying the course of AD. Currently, AD has no cure. A breakthrough in treatment that modifies the underlying AD disease process would be a major achievement with enormous medical and social benefits. Little is known concerning older Americans' perceptions about AD and their willingness to accept risk to avoid AD. METHODS: American residents aged 60 years and older who have not been diagnosed with AD, and are not taking prescription medicines to treat AD, memory problems or dementia completed an online survey questionnaire that included a series of stated-choice trade-off tasks. Respondents chose between pairs of hypothetical treatment alternatives, each including different 7-year AD disease-progression profiles and risks of serious adverse events that would result in death or severe disability. We used mixed-logit methods to estimate the maximum acceptable risk (MAR) of serious adverse events that would result in death or severe disability. RESULTS: 2,146 respondents completed the survey. Mean (SD) age was 70 (7.4). In return for preventing AD from progressing beyond the mild stage, the mean MAR (95% CI) was 46.8% (40.3%-54.3%); that is older Americans were willing, on average, to accept an increase in the risk of death or severe disability from stroke of nearly 50% to avoid progression to the moderate and severe stages of AD. CONCLUSION: Older Americans' willingness to accept significant increases in the risk of death or disability in exchange for treatments that modify the course of AD indicates the value of such treatment benefits.