BACKGROUND: Postural stability can be measured in clinical and research settings using portable plantar pressure systems. People with rheumatoid arthritis (RA) have decreased postural stability compared to non-RA populations and impaired postural stability is associated with falls in people with RA. The purpose of this study was therefore to investigate the reliability of the TekScan MatScan® system in assessing postural stability in people with RA. METHODS: Twenty three participants with RA, mean (SD) age 69.74 (10.1) years, were assessed in barefoot double-limb quiet standing, with eyes open and eyes closed, for antero-posterior and medio-lateral postural sway values. Three repetitions, at a sampling frequency of 40 Hz, were recorded for each test condition to obtain a mean value. Measurements were repeated one hour later. Intraclass correlation coefficients (ICC) with 95% confidence intervals (CI) were calculated to determine between-session reliability. Measurement error was assessed through the calculation of the standard error of the measurement (SEM) and the smallest real difference (SRD). RESULTS: The system displayed good to excellent reliability for antero-posterior and medio-lateral sway, with eyes open and closed, as indicated by ICC values ranging from 0.84 to 0.92. Measurement error, as evidenced by the SEM, ranged from 1.27 to 2.35 mm. The degree of change required to exceed the expected trial to trial variability was relatively high, compared to mean values, with SRD ranging from 3.08 to 5.71 mm. CONCLUSIONS: The portability and ease of use of the TekScan MatScan® makes it a useful tool for the measurement of postural stability in clinical and research settings. The TekScan MatScan® system can reliably measure double-limb quiet standing in older people, aged 60 to 80 years, with RA.