Hyperhomocysteinemia is an independent risk factor for cardiovascular, cerebrovascular and peripheral vascular diseases that are complicated by atherosclerosis and a thromboembolism. An increased level of plasma homocysteine develops from a genetic defect in the of enzyme for the homocysteine metabolism or a vitamin deficiency. Hyperhomocysteinemia has direct toxic effect on the vascular endothelium and causes damages to the antithrombotic action of vascular endothelial cells. Most cases of hyperhomocysteinemia are asymptomatic, but cardiopulmonary or cerebrovascular incidents developin rare cases. In the case of a thromboembolism with an unknown cause, hyperhomocysteinemia should be considered in a differential diagnosis. The authors report a case of pulmonary thromboembolism in a patient with hyperhomocysteinemia with a review of the relevant literature.