The nature and severity of behavioral problems, and their relationship to cognitive and functional abilities, was investigated in 56 community-residing patients with Alzheimer's disease. Measures evaluated three domains of function: behavior, cognition and activities of daily living. Problems of cognitive functioning, such as memory loss, confusion, and disorientation were most prevalent, reported to occur in 84%, 82%, and 64% of the sample, respectively. Problems with activity and emotional distress were next, affecting 20 to 43% of the sample. The mean number of problems reported was 10 per patient. Twenty-two percent of caregivers reported a minimum of 15 problems occurring at least twice a week and no caregiver reported an absence of problems. Male patients were reported to have more behavioral difficulties. Level of behavioral disturbance was largely unrelated to cognitive or functional ability. Age was unrelated to cognitive or behavioral disturbance but significantly related to activities of daily living. Results indicated that behavioral problems are prevalent and pervasive in even moderately impaired community-residing Alzheimer disease patients, and that age may be more important than level of cognitive dysfunction in predicting difficulties with activities of daily living.