Abstract: AIM: To investigate the relationship between day-night rhythm of blood pressure and ambulatory arterial stiffness index (AASI) in hypertensive elderly subjects. METHODS: According to the monitoring result of ambulatory blood pressure, 112 patients were divided into three groups: dippers (n=37), non-dippers (n=45), and reverse-dippers (n=30). AASI was determined in all the patients. RESULTS: No significant differences were found among the three groups in age, body mass index, serum total cholesterol, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, fasting blood glucose, 24-h mean systolic blood pressure (SBP), 24-h mean diastolic blood pressure (DBP), daytime mean SBP, day time SBP, and day time mean DBP. However, significant differences were found in nighttime mean SBP, nighttime mean DBP and AASI among the three groups (P<0.01). CONCLUSION: Day/night rhythm of blood pressure and AASI are closely correlated in hypertensive elderly subjects.