Elevated fasting plasma homocysteine is a graded and independent risk factor for coronary and other forms of vascular disease. It has been recently demonstrated that the two common mutations in the gene encoding for the methylenetetrahydrofolate reductase (MTHFR) leading to the production of a thermolabile enzyme variant. This study conducted on 40 patients divided into group (1): 20 CAD patients and group (2): 20 CVS patients, compared with 20 healthy control subjects. This study concluded that the TT and CT genotypes were associated with increased plasma homocysteine above 15 umol/L was a significant risk factor for the presence of CAD and CVS.