BACKGROUND: The measurement of functional disabilities in patients with dementia is one of the essential parts of evaluation for dementia from the viewpoint of diagnosis and therapeutic intervention. Nevertheless, few standardized scales for the instrumental activities of daily living (IADL) are available in Korea. The purpose of this study was to test the reliability and validity of the Korean IADL (K-IADL). METHODS: K-IADL is comprised of 11 items that were selected by the Representative Committee of the Korean Dementia Research Group. These include: (1) shopping, (2) mode of transportation, (3) ability to handle finances, (4) house keeping, (5) preparing food, (6) ability to use a tele-phone, (7) responsibility for own medication, (8) recent memory, (9) hobbies, (10) watching television, and (11) fixing around the house. K-IADL was administered to informants of 114 dementia patients and age and sex matched 106 con-trols. The informants rated each item as follows: 0=normal, 1=with some assistance, 2=with much assistance, 3=unable to do, NA=not applicable. RESULTS: Internal consistency (Cronbach's alpha=0.96) and the test-retest reliability(r=0.94) of K-IADL were significant. A principle component factor analysis extracted a single factor that accounted for 70.3% of the total variance (Eigenvalue: 7.74), and K-IADL was correlated significantly with other general cognitive indices, demonstrating good validity. With a cut-off point of 0.43, the K-IADL had a sensitivity of 83% and a specificity of 82% in the diagnosis of dementia. CONCLUSIONS: Our results showed that K-IADL could be a reliable and valid tool for the quantification of functional disabilities of Korean dementia patients.