Abstract: This study was aimed to evaluate the association of serum homocysteine with peripheral atherosclerosis and deep vein thrombosis in an Iranian population complaining from vascular symptoms in lower limbs referred to a university general hospital in the capital of Iran. The study design was case-control. Deep vein thrombosis and atherosclerosis groups were, respectively consisted of 25 patients presenting with signs and symptoms of deep vein thrombosis whom disease was confirmed by duplex ultrasonography and 25 patients presenting with signs and symptoms of chronic arterial insufficiency who were candidate for arterial reconstruction whom disease was confirmed by angiography. The control group was consisted of 25 persons selected among relatives accompanying the traumatic patients admitted in the general surgery ward of the same hospital. The age of atherosclerosis, DVT and control group were 61±14, 47±16 and 40±14, respectively. The serum level of homocysteine was higher in males (p<0.01) except for atherosclerotic patients. The prevalence of high homocysteine was 15% (control), 36% (DVT) and 56% (atherosclerosis) among females and 75% (control), 73% (DVT) and 56% (atherosclerosis) among males. The serum homocysteine in the control group which was representative of Tehran population who do not take vitamin B supplements was unexpectedly high. It seems that fortification of popular foodstuffs should be considered for Tehran. The association between homocysteine and atherosclerosis and deep vein thrombosis was not confirmed in this study especially for men who had higher serum homocysteine than women. It is possible that this association fades away in populations with high prevalence of hyperhomocysteinema.