Background and Objectives: Prior research has documented that Alzheimer's disease (AD) is associated with increased costs from comorbid conditions. However, little is known about medical resource utilization and costs among AD patients prior to the onset of cognitive symptoms. This study estimates excess acute care costs among Medicaid AD patients in the year prior to diagnosis. Study Design: Administrative claims data for New Jersey Medicaid patients over the period 1997-2010 were retrospectively analyzed. The study focused on non-institutionalized AD patients and examined their medical costs compared with matched controls with no dementia over the 12 months prior to their preliminary diagnosis. Costs reflect amounts reimbursed by Medicaid to medical service providers, reported in 2010 US dollars. Results: The study sample included 11,536 AD patients who were matched to controls. Average age was 76 years, and 76.2 % were female. Compared with matched controls, total medical costs over the 12-month pre-index period were US$ 5,549 higher among AD patients (US$ 14,977 vs. US$ 9,428, p < 0.001), of which US$ 3,321 (p < 0.001) was due to outpatient services. Home care and medical daycare services accounted for US $1,442 (p < 0.001) of the difference. Emergency department visits and inpatient care accounted for only a small fraction of the excess costs. Conclusions: Compared with controls, Medicaid AD patients incurred higher acute care costs in the 12 months prior to their preliminary diagnosis, suggesting room for beneficial interventions and better disease management should earlier diagnosis become possible. These findings may be especially relevant in light of new criteria facilitating earlier diagnosis of AD. © 2013 Springer International Publishing Switzerland.