Background: Seasonal variations in blood pressure (BP) among hypertensive patients may be responsible for the higher mortality from cardiovascular disease in winter. However, it is not yet clear what factors are relevant to the seasonal BP changes. We assessed the hypothesis that arterial stiffness is related to the mean BP changes between summer and winter. Methods: Eighty five old adult (>55 years) patients with essential hypertension (33 males, 64짹6.0 years) were enrolled. Seasonal BP profiles for at least 2 years were studied along with arterial stiffness (brachial-ankle pulse wave velocity measured by oscillometric technique), clinical variables (age, gender, smoking, duration of hypertension, anti-hypertensive medications and body mass index) and echocardiographic variables. Results: Both systolic and diastolic mean BP were significantly higher during winter compared to other three seasons (spring; 128짹10.0/79짹7.3mmHg, summer; 127짹9.8/78짹7.1mmHg, autumn; 127짹10.3/78짹8.0 mmHg, winter; 136짹12.5/81짹7.6mmHg, systolic BP changes; p<0.001, diastolic BP changes; p<0.001). There were no significant seasonal difference among spring, summer, and autumn. The pulsed wave velocity was correlated with seasonal winter - summer differences in systolic BP (r=0.272, p=0.012), but not in diastolic BP (r=0.188, p=0.085). Age, which was correlated with pulsed wave velocity strongly (p<0.001), were not related to the seasonal changes in BP (systolic BP changes; p=0.114, diastolic BP changes; 0.298). No other clinical variables were shown to have a significant correlation with seasonal BP changes. Conclusions: Both systolic and diastolic BP were highest during winter. Our results establish a feasible link between arterial stiffness and seasonal BP variations. These findings may be partly explanatory of higher cardiovascular risk in patients with increased arterial stiffness.