BACKGROUND: The limitation of activities of daily living (ADL) is a critical problem in dementia patients in addition to cognitive dysfunction. In spite of many previous studies about the relationship between cognitive dysfunction, ADL and the nature of functional changes, there have not been any clear explanations about the liaisons between them due to various results from the diversity of objects and methods. The purpose of this study is to evaluate the relationship between ADL and clinical features in patients with Alzheimer's disease. METHODS: One hundred thirty-four patients with Alzheimer's disease were enrolled to participate in the study. The physical activity of daily living (P-ADL) and the Korean instrumental activity of daily living (K-IADL) were evaluated in the patients. In addition, all subjects were tested by a Korean version of the expanded clinical dementia rating scale (CDR), and a Korean version of the mini-mental state examination (K-MMSE) and a Korean version of the neuropsychiatric inventory (NPI). RESULTS: ADL was significantly correlated with cognitive functioning (r>-0.75, p<0.01). NPI was not significantly correlated with P-ADL and KIADL. The ability to use the telephone was the most highly correlated with CDR and K-MMSE (r>0.72, p<0.01). The ability to use the telephone was the most predictable item in K-IADL and bathing was the most predictable item in PADL. The deterioration of K-IADL showed rapid progression in the degree of CDR 2 and P-ADL showed rapid progression in the degree of CDR 4, respectively. CONCLUSIONS: The ADL decline induced by dementia may progress and have a close correlation with clinical manifestations of dementia including cognitive dysfunction, behavioral symptoms and psychological symptoms.