OBJECTIVES: To understand the range of symptoms that present to family caregivers of community-dwelling persons with Alzheimer's disease and related dementias (ADRD). DESIGN: Six-month longitudinal prospective study to identify the incidence of new or worsening symptoms and their association with acute care medical service use. SETTING: Community-based sample of volunteers from multiple states. PARTICIPANTS: A total of 136 patient-caregiver dyads with a range of dementia severity. MEASUREMENTS: Forty four symptoms and signs common in older persons and/or persons with dementia; frequency of emergency department visits, hospitalizations, and death; and associations between reported symptoms and acute medical care. RESULTS: During a mean of 5.7 months' follow-up, new or worsening organ-specific (90% of participants), nonspecific (89%), and behavioral (88%) symptoms were common, with the average caregiver reporting seven new or worsening symptoms. Most common were worsening confusion (74%), decreased activity (64%), agitation (57%), hallucinations/delusions (45%), voice and speaking problems (45%), not eating or drinking (44%), and stress/anxiety (41%). Hospitalization and emergency department use occurred respectively in 19% and 20% of participants, and were associated with organ-specific symptoms (OR 3.15, P = .02), less so with nonspecific symptoms (OR 2.27, P = .07), and very little with behavioral symptoms (OR 1.44, P = .38). Within each symptom category, certain symptoms were significantly associated with acute medical service use. CONCLUSION: Family caregivers of persons with ADRD must respond to a variety of medical, nonspecific, and behavioral symptoms. The high incidence of new or worsening symptoms and of acute medical care use suggests a need to better target symptom evaluation and management in caregiver education.