Functional ability evaluation constitutes an important outcome measurement in any proposed trial involving patients with rheumatoid arthritis (RA). We performed a crosscultural study directed at the translation into Portuguese of the Physical Ability Dimension of the Health Assessment Questionnaire (HAQ) and the evaluation of its reliability. Five questions were modified in the Portuguese version of the HAQ to suit Brazilian conditions. The test-retest correlation coefficient was 0.905 (p less than 0.001) and the interobserver correlation coefficient was 0.830 (p less than 0.001) Our results provide evidence of instrument reliability. The instrument kept its face and content validity and the evaluation of the longitudinal construct validity is now in progress.