['Seasonal variation in blood pressure (BP), a usual tendency of both systolic (SBP) and diastolic BP (DBP) to rise during winter in hypertensive patients, may be related to the higher cardiovascular mortality in winter. However, it is not yet clear what factors are relevant to the seasonal BP changes. We hypothesized that arterial stiffness is related to the BP changes between summer and winter.', 'Eighty-five elderly (>55 years) patients with essential hypertension (33 males, 64+/-6.0 years) were enrolled. Seasonal BP profiles over at least 2 years were studied along with arterial stiffness and clinical variables (age, gender, smoking, duration of hypertension, anti-hypertensive medications and body mass index). Both SBP and DBP were significantly higher during winter compared with three other seasons (spring 128+/-10.0/79+/-7.3 mmHg, summer 127+/-9.8/78+/-7.1 mmHg, autumn 127+/-10.3/78+/-8.0 mmHg, winter 136+/-12.5/81+/-7.6 mmHg; SBP changes; p<0.001, DBP changes; p<0.001). There were no significant seasonal differences among spring, summer and autumn. Pulse wave velocity (PWV), a widely used clinical indicator of arterial stiffness was correlated with winter-summer differences in SBP (r = 0.272, p = 0.012), but not in DBP (r = 0.188, p = 0.085). Age, which was correlated with PWV strongly (p<0.001), was not significantly related to the seasonal changes in BP (SBP changes; p = 0.114, DBP changes; p = 0.298). No other clinical variables had significant correlation with seasonal BP changes. Multivariate regression analysis revealed that PWV is the only significant predictor for winter-summer SBP changes.'] Is arterial stiffness related to augmented seasonal variation of blood pressure in hypertensive patients?