Abstract: Objective: To investigate homocysteine（HCY） concentration in ischemic stroke patients and in coronary heart disease（CHD） patients in comparison with normal controls and to evaluate whether providing folate and vitamin B12 could decrease serum homocysteine concentration.Methods: Serum HCY levels of 60 patients with cerebral infarction（CI） and 60 patients with CHD and 60 normal controls were measured.Then each group was randomly divided into two groups in which one group was provided with folate 5mg qd,and vitamin B12 250μgtid while the other was not provided with folate and vitamin B12.These patients were reexamined after 2 months.Results: The mean serum HCY level was（16.5±5.4）μmol/L for cerebral infarction patients,（14.5±4.9） μmol/L for CHD,and（12.1±2.9） μmol/L for normal subjects.Statistically,the mean serum HCY levels of cerebral infarction and CHD patients were significantly higher than those of the normal subjects（P＜0.01）.The HCY concentration was lower in the groups provided with foliate and vitamin B12 than that in the groups without folate and vitamin B12（P=0.0001）,even in the normal youngers.Conclusions: The HCY concentration is higher in the patients with ischemic stroke or CHD.Folate supplement could moderately lower HCY.