OBJECTIVE: The goal of this study was to define the recurrence or continuation of neuropsychiatric symptoms in patients with Alzheimer's disease who were observed serially for a 1-year period. METHOD: One hundred eighty-one patients with probable Alzheimer's disease were assessed five times at 3-month intervals with a standardized neuropsychiatric rating instrument. RESULTS: Recurrence rates of neuropsychiatric symptoms during the 1-year period were 85% for depression, 93% for agitation, and 95% for psychosis. Symptom frequency at any point in time underestimated the cumulative 1-year frequency. Recurrence rates were significantly greater among patients who had multiple symptoms. Women exhibited more symptoms than men. Patients in the oldest age group (76-87 years) had more psychosis, less depression and agitation, and slower cognitive decline. Psychosis was associated with more rapid cognitive decline, and agitation was associated with more rapid functional deterioration. CONCLUSIONS: These results indicate that once psychiatric symptoms are present in patients with Alzheimer's disease, they frequently recur. These symptoms vary with age, sex, and rate of illness progression.