Management of behavioral symptoms in patients with age-associated dementia is essential to improve quality of life for them and their caregivers. Although many results have been reported about the burden on caregivers of demented relatives, no guidelines for managing behavioral symptoms of demented patients have been developed. One of the major reasons for the lack of practical guidelines is that dementia behavioral syndromes have been understood to be a socio-psycho-somato disorder. Also, no standardized procedures to assess behavioral symptoms are yet available. In this article, the relationship of behavioral symptoms to the severity of dementia is examined by different assessment procedures, with the aim of understanding their manifestation mechanisms. In 223 patients with age-associated dementia, including 99 with Alzheimer type dementia, 32 behavioral symptoms were assessed according to frequency, severity, and intensity, which was assessed corresponding to a value score multiplied by a frequency score multiplied by a severity score. The results by an analysis of covariance with intensity, frequency, and severity of symptoms as dependent variables; severity of dementia as an independent variable; and age, sex, and activities of daily living scores as covariates, indicated that some behavioral symptoms are significantly related to severity of dementia, which is hypothesized to correspond to organic changes in the brain, while other symptoms are not related to severity of dementia. Also, the pattern of relationship varied according to assessment procedures.(ABSTRACT TRUNCATED AT 250 WORDS)