Katz' Index of ADL has been supplemented by five well-defined instrumental activities, namely cooking, washing, transportation, cleaning, and shopping. Eighty-five persons, mainly elderly, who had consecutively consulted a district occupational therapist, were assessed in their homes in order to study the reliability, the scalability, and the validity of the expanded index. The inter-observer reliability was high. The coefficient of scalability was well above the acceptance level, indicating construct validity. No person was dependent in personal ADL and totally independent in instrumental ADL. Persons who were dependent in both personal and instrumental ADL were older and lived in sheltered accommodation more often than persons who were dependent only in instrumental ADL, indicating external validity. This study shows that there was a cumulative relationship between certain well-defined instrumental activities and between personal and instrumental activities. This supplemented index can be useful for assessing and differentiating the need for personal assistance and homecare among disabled elderly people.