Homocystinuria is an inborn error of methionine metabolism and has several causes. Among the causes, cystathionine-b-synthase deficiency is the most common. The major clinical manifestations are ectopia lectis skeletal deformities, mental retardation and occlusive vascular disease A 16 year old girl was admitted with generalized seizure. She had a history of bilateral lens dislocation and thoracic scoliosis. Her brain MRI and MRA showed mass-like lesions at both frontal area and diffuses, stenosis of the right internal carotid artery She underwent a stereotaxic brain biopsy and cerebral angiography. Two days, after angiography, she was suddenly aggravated to show stuporous mentality and quadriplegia. FoIlow-up brain MRI showed newly developed acute ischemic lesions at both parietal area MR venography confirmed superior sagittal sinus thrombosis. Methionine and homocystine were markedly elevated in plasma and 24 hour urine. She recovered with anticoagulation and vitamin supplementation(folate and pyridoxine). Homocystinuria should be suspected in stroke patients of young age, especially if thy have nontraumatic lens dislocation or marfanoid features. We report a patient with homocystinuria complicated by cerebral venous sinus thrombosis which was aggrevated after cerebral angiography.