Objective: Masked hypertension is a clinical condition, the importance of which is agreed in recent years and which is characterized by increased cardiovascular mortality and morbidity and is thought to be important endothelial dysfunction in the pathophysiology. Plasma total homocysteine levels are accepted as a major independent biomarker for endothelial dysfunction and/or a contributor to hypertension and coronary artery disease. In this study, we aimed to measure the level of serum homocysteine and to evaluate the relationship between the parameters of ambulatory blood pressure monitoring in patients with masked hypertension. Methods: This cross-sectional observational study included 37 subjects with normal blood pressure, 30 with masked-hypertension and 27 patients with obvious hypertension. Masked hypertension (MHT) was defined as office blood pressure <140/90 mm Hg and mean daytime ambulatory systolic blood pressure in 24 hours monitoring ≥135/85 mm Hg. Homocysteine levels of the subjects were measured by using HPLC system with fluorescent detector. Lipid parameters were measured by routine methods. Mann-Whitney U test was used for statistical analysis. Results: In the analysis of homocysteine, it was observed that there was no difference between the control group and patients with masked hypertension. Patients with high blood pressure showed higher homocysteine levels when compared to masked hypertension (p=0.02). Homocysteine levels showed a weak positive correlation with average systolic blood pressure (r=0.335, p=0.043). Homocysteine levels were higher in smokers than non-smokers. compared with non-smokers group in all participants (p=0.036). Conclusion: We have reached the opinion that in the individuals with no obvious health problems but with masked hypertension, homocysteine levels may not have any significant effect upon high blood pressure levels. © 2014 by Turkish Society of Cardiology.