Behavioral problems are thought to be pervasive and devastating to patients with dementia of the Alzheimer's type and their families. Despite this, little empirical data are available concerning the nature of such impairments, their rate of occurrence or their relationship to the disease process. This study investigated 127 patients with a primary diagnosis of dementia of the Alzheimer's type. Two methods of behavioral assessment were employed: a standardized dementia rating scale and a checklist of behavioral problems. Results indicated a) the overall number of problems significantly increased with increased cognitive impairment, b) the types of problems reported varied with cognitive severity, and c) behavioral problems were not significantly associated with patient's age, gender, duration, or age at onset of dementia. These findings are discussed as they relate to the phenomenology of dementia of the Alzheimer's type and to suggestions for interventions at different stages of the disease process. Problems found associated with level of impairment such as wandering, agitation, incontinence, and poor personal hygiene are thought to be characteristic of the disease and therefore predictable. Problems found not associated with level of impairment such as hallucinations, irrational suspicions, falls, and restlessness are likely to be idiosyncratic. The former should probably be incorporated into education and intervention programs; the latter addressed as needed on an individual basis.