Objective: The objective of this study was to investigate change over time in financial abilities in patients with mild Alzheimer disease (AD). Methods: The authors conducted a prospective 1-year longitudinal study at a large southern U.S. metropolitan-area medical school university. Participants included healthy older adults (N=63) and patients with mild AD (N=55). The authors conducted a standardized performance measure of financial capacity. Performance was assessed on 18 financial tasks, nine domains of financial activity, and overall financial capacity. Capacity outcomes classifications (capable, marginally capable, or incapable) for domains and overall performance were made using cut scores referenced to comparison group performance. Results: At baseline, patients with mild AD performed significantly below healthy older adults on 16 of 18 tasks, on all nine domains, and on overall financial capacity. At one-year follow up, comparison group performance was stable on all variables. In contrast, patients with mild AD showed substantial declines in overall financial capacity, on eight of nine domains, and on 12 of 18 tasks. Similarly, the proportion of the mild AD group classified as marginally capable and incapable increased substantially over one year for the two overall scores and for five financial domains. Conclusions: Financial capacity is already substantially impaired in patients with mild AD at baseline and undergoes rapid additional decline over one year. Relative to the comparison group, overall financial capacity performance in the AD group declined 10%, from approximately 80% of the comparison group performance atbaseline to 70% at follow up. Financial skills showed differential rates of decline on both simple and complex tasks. Of clinical and public policy interest was the declining judgment of patients with mild AD regarding simple fraud schemes. The study supports the importance of prompt financial supervision and planning for patients newly diagnosed with AD. © 2008 American Association for Geriatric Psychiatry.