Different tools are available for the measurement of functional status; however, only a few of them are based on the evaluation of the joint range of motion (ROM). This study is aimed at the design and evaluation of the measurement properties of a ROM scale to be used as an evaluative instrument in rheumatoid arthritis (RA) trials. The EPM-ROM Scale evaluates 10 distinct movements of the small and large joints. The score of each joint varies from 0 (full movement) to 3 (severe limitation) and the cut-off degrees of motion are, in general, based on the lack of ability to perform some determined activities of daily living. The test-retest characteristic of the scale was assessed by administering the scale twice, 5 days apart, to 35 RA patients. The product moment correlation was 0.775 (P less than 0.001). The cross-sectional construct validity of the scale was assessed by the concomitant scoring of the EPM-ROM Scale and the functional ability dimension of the Health Assessment Questionnaire (a reliable, valid and responsive instrument) in these patients. The product moment correlation was 0.518 (P less than 0.001). The evaluation of its longitudinal construct validity and responsiveness are now in progress.