The purpose of this study was to evaluate an instrument for assessment of physical disability, mainly intended for clinical settings, the Disability Rating Index (DRI). Healthy persons (n = 1092), both white and blue collar workers, and patients (n = 366) with different levels of physical capacity, were assessed. Most of the patients (n = 303) underwent rehabilitation programmes for neck/shoulder/low-back pain but some (n = 47) were arthritis patients waiting for hip or knee replacement surgery, or wheelchair patients with multiple sclerosis (n = 16). The reliability was investigated by test-retest studies, intra- and inter-rater and internal consistency studies. Five construct validity tests were carried out: a discrimination study; a converging validity test; a test for sensitivity to small alterations in health status; and two correlational validity tests. Correlation of the self-reported DRI to the actual performance in similar activities was carried out. Responsiveness was tested by correlation of the DRI before/after replacement surgery for arthritis. The test-retest correlations were 0.83-0.95 in the studies, including correlation of different versions. The intra- and inter-rater reproducibility was 0.98 and 0.99 respectively. The Kruskal-Wallis test in the discrimination study yielded p < 0.0001. More than 90% of the respondents completed the questionnaire correctly. Correlation of the DRI to the Functional Status Questionnaire was 0.46. The responsiveness was excellent, p = 0.0001. The DRI proved to be a robust, practical clinical and research instrument with good responsiveness and acceptability for assessment of disability caused by impairment of common motor functions.