Background: Neuropsychiatric symptoms are nearly universal in dementia, yet little is known about their longitudinal course in the community. Objective: To estimate point and 5-year period prevalence of neuropsychiatric symptoms in an incident sample of 408 dementia participants from the Cache County Study. Methods: The Neuropsychiatric Inventory assessed symptoms at baseline and at 1.5 years, 3.0 years, 4.1 years, and 5.3 years. Point prevalence, period prevalence and mean symptom severity at each time point were estimated. Results: Point prevalence for delusions was 18% at baseline and 34-38% during the last three visits; hallucinations, 10% at baseline and 19-24% subsequently; agitation/aggression fluctuated between 13% and 24%; depression 29% at baseline and 41-47% subsequently; apathy increased from 20% at baseline to 51% at 5.3 years; elation never rose above 1%; anxiety 14% at baseline and 24-32% subsequently; disinhibition fluctuated between 2% and 15%; irritability between 17% and 27%; aberrant motor behavior gradually increased from 7% at baseline to 29% at 5.3 years. Point prevalence for any symptom was 56% at baseline and 76-87% subsequently. Five-year period prevalence was greatest for depression (77%), apathy (71%), and anxiety (62%); lowest for elation (6%), and disinhibition (31%). Ninety-seven percent experienced at least one symptom. Symptom severity was consistently highest for apathy. Conclusions: Participants were most likely to develop depression, apathy, or anxiety, and least likely to develop elation or disinhibition. Give converging evidence that syndromal definitions may more accurately capture neuropsychiatric co-morbidity in dementia, future efforts to validate such syndromes are warranted.