Hyperhomocysteinemia (HHcy) is an independent risk factor of vascular diseases. The occurrence of HHcy can be attributed to genetic factors, diet, life style and some individual factors. HHcy is closely associated with hypertension. Recently large amounts of studies have demonstrated that the end-organ damage is more closely related to 24-hour blood pressure variability than to single blood pressure values. Thus, the relationship between HHcy and blood pressure variability has been an important research issue. Recent studies have revealed that a higher serum homocysteine level is an independent risk factor for increased blood pressure variability. The mechanism of increased blood pressure variability caused by HHcy could be the activation of the renin-angiotensin system, induction of the dysfunction of the cardiovascular autonomic system, and exacerbation of atherosclerosis.