In order to measure disability in the elderly with a variety of handicaps a comprehensive activities of daily living (ADL) index is described. This instrument, named the ADL-20, consists of 20 items from four major categories of daily activities: (1) 5 items from basic ADL for mobility (BADLm), (2) 6 items from basic ADL for self-care (BADLs), (3) 7 items from instrumental ADL (IADL), and (4) 2 items from communication ADL (CADL). Each activity is scored on a four point scale with values from 0 (total dependency) to 3 (independency). In order to study the interrater reliability of the instrument 40 subjects were examined by a physician and physiotherapist independently at the University of Tokyo Hospital on the same day. Perfect agreement rates on the assignment of the disability score ranged from 70.0% to 97.5% with 85.6% in 800 paired examinations. The kappa values for perfect agreement ranged from 0.52 to 0.88. These results may guarantee a moderate or greater degree of interrater reliability. The correlation coefficients of the Spearman test on the rating scores by the physician and physiotherapist ranged from 0.66 to 0.99 in each activity with 0.97 in total score of 20 items. This scale was employed in 110 patients at the University Hospital and 106 patients staying in the nursing home or long-stay geriatric hospital in order to study its validity. The average age of those 216 patients, 77 males and 139 females, was 76.2 years old. The Cronbach alpha value concerning the consistency of each item as ADL assessment scale was 0.97.(ABSTRACT TRUNCATED AT 250 WORDS)