The present study aimed to evaluate the utility of the activities of daily living (ADL) index for partially dependent elderly people (ADL-PDI) when applied longitudinally to an institutionalized partially dependent (PD) group, and to determine the characteristics of the longitudinal change in ADL ability of the PD group. The subjects were ten Japanese PD living at welfare institutions for the aged such as accredited nursing homes and health facilities (mean age was 82.2 ± 2.32 years in total; 84.3 ± 4.18 years for five males; 80.3 ± 2.33 years for five females). The questionnaire consisted of the ADL-PDI, the Barthel index (BI), physical independence, dementia independence, anamnesis, body impairments, use of assisting devices, the institutionalized period, and type of medical rehabilitation and medical treatment, and was administered to the subjects twice during their institutionalized period. All testers were staff working at the subjects' institution, such as occupational therapists, physiotherapists and nurses. The result of the longitudinal ADL assessment was that ADL-PDI may evaluate the longitudinal change in ADL ability on a unidimensional scale. The utility of the standard for discriminating the functional level of the elderly using the ADL-PDI score, which was indicated in our previous study (Sato et al., 2001), was supported by longitudinal data. Furthermore, the BI was superior to the ADL-PDI in evaluating the disabled elderly with lower functional levels. However, the ADL-PDI was better than the BI in evaluating the disabled elderly with a higher functional level and was considered to have wider applications in evaluating the ADL ability of the elderly.