Abstract: There have been many controversial debates on the role of Hyperhomocysteinaemia (HHcy) as an independent risk factor for Coronary Artery Disease (CAD) during recent years. Furthermore, an alanine/valine (Ala/Val) gene polymorphism at 222nd amino acid of 5,10-methylenetetrahydrofolate reductase (MTHFR) has been considered as a factor that could render this enzyme thermolabile and less active which in turn may yield a subsequent increase in plasma total homocysteine (tHcy) levels. To assess whether this polymorphism is associated with increased risk of CAD and plasma levels of tHcy in a population from southern Iran, a total of 457 patients with angiographically documented multi-vessel CAD were compared with a control group comprised of 371 subjects with <30% stenosis in all major vessels. Nevertheless our results failed to admit a significant difference between CAD individuals and control subjects for Ala/Val polymorphism and plasma Hcy concentrations. However, plasma Hcy concentrations were significantly higher in individuals with Val/Val genotype than subjects with Ala/Ala genotype, but it didn’t show a significant association with CAD in our population. Moreover, as the multiple linear regression analysis indicated, smoking habit, folate levels and the MTHFR Val/Val genotype were the only major predictors of tHcy concentrations in the current investigation.