However, studying about the 24-hour blood pressure variation in Vietnamese people have not been paying much attention. Objectives: Studying the 24-hour blood pressure variation in the primary hypertensive patients with metabolic syndrome. Methods: Prospective, cross-sectional study. Results: In this study, 54 HBP patients with MS and 44 HBP patients without MS (control group) at the same age have been taken blood pressure and 24 hour blood pressure by Ambulatory Blood Pressure Monitoring (ABPM).