The objectives were to investigate whether there is a discordance between observed and reported functional ability in patients with rheumatoid arthritis (RA) as measured by the Health Assessment Questionnaire (HAQ) and, if so, which demographic, clinical and psychological factors contribute to that discordance. Fifty-one consecutive RA patients of the out-patient clinic were included. Self-reported functional ability was compared with the observed performance of tasks as described by the HAQ. The amount of discordance was computed by subtracting reported scores from observed scores. A positive sign stands for overestimation of functional ability by the patient. The average amount of discordance was low, 0.09 (S.D. 0.39), but showed a large range: -0.88 to 1.00. Multiple regression analysis showed that male patients overestimate their functional ability by 0.21 HAQ units compared with female patients. RA patients overestimate their functional ability with increasing disease duration and severity, while RA patients in the early stage of the disease tend to underestimate their functional ability.