Objectives: To determine family caregivers' willingness to use Alzheimer's disease (AD)-slowing medicines and to examine the relationships between this willingness, dementia severity, and caregiver characteristics. Design: Cross-sectional survey. Setting: In-home interviews of patients from the Memory Disorders Clinic of the University of Pennsylvania's Alzheimer's Disease Center. Participants: One hundred two caregivers of patients with mild to severe AD who were registered at an Alzheimer's disease center. Measurements: Subjects participated in an in-home interview to assess their willingness to use a risk-free AD-slowing medicine and a medicine with 3% annual risk of gastrointestinal bleeding. Results: Half of the patients had severe dementia (n=52). Seventeen (17%) of the caregivers did not want their relative to take a risk-free medicine that could slow AD. Half (n=52) did not want their relative to take an AD-slowing medicine that had a 3% annual risk of gastrointestinal bleeding. Caregivers who were more likely to forgo risk-free treatment of AD were older (odds ratio (OR)=1.7, P=.04), were depressed (OR=3.66, P=.03), had relatives living in a nursing home (OR=3.6, P=.02), had relatives with more-severe dementia according to the Mini-Mental State Examination (MMSE) (OR=2.29, P=.03) or Dementia Severity Rating Scale (DSRS) (OR=2.55, P=.002), and rated their relatives' quality of life (QOL) poorly on a single-item global rating (OR=0.25, P=.001) and the 13-item quality-of-life (QOL)-AD scale (OR=0.38, P=.002). Caregivers who were more likely to forgo a risky treatment were nonwhite (OR=6.53, P=.005), had financial burden (OR=2.93, P=.02), and rated their relative's QOL poorly on a single-item global rating (OR=0.61, P=.01) and the QOL-AD (OR=0.56, P=.01). Conclusion: These results suggest that caregivers are generally willing to slow the progression of their relative's dementia even into the severe stage of the disease, especially if it can be done without risk to the patient. Clinical trials and practice guidelines should recognize that a caregiver's assessment of patient QOL and the factors that influence it affect a caregiver's willingness to use AD-slowing treatments.