To study the distensibility and the diameter of the abdominal aorta and the common carotid artery (CCA) in patients with rheumatoid arthritis (RA), and investigate the relation between mechanical properties of these arteries and disease severity. One hundred and one patients with RA (33 consecutive cases with extra-articular manifestations, and 68 subjects with non-extra-articular disease, matched for age, sex and disease duration) were investigated. Echo-tracking ultrasonography was used to measure stiffness and mean diameter of the abdominal aorta and the CCA. The patients were compared with healthy individuals from the corresponding age group (n=74 for measurements of the aorta, n=64 for the CCA). Predicted values for stiffness and mean diameter, based on age and sex, were calculated. Stiffness of the abdominal aorta was increased in women with RA [mean percentage of predicted value (% predicted) 180; 95% confidence interval (95% CI) 150-211] but not in men (% predicted 99; 95% CI 75-122). CCA stiffness was less markedly increased, and mean diameters of the aorta and the CCA were not different from the expected. In the RA cohort, patients with extra-articular manifestations tended to have greater stiffness of the aorta (P=0.11), and disability, as indicated by a higher Health Assessment Questionnaire score, was associated with increased aortic stiffness (P=0.04). RA is associated with decreased distensibility of the abdominal aorta in females, and such changes seem to correlate with disease severity. We suggest that arterial stiffness is an important factor in cardiovascular co-morbidity in RA.