Design:
Double-blind, multicenter, randomized, controlled clinical trial

Inclusion Criteria
Patients who presented within 120 days of an NCDI with symptoms lasting more than 24 hours, or with a CT or MRI-visualized infarct, who had a modified Rankin scale (MRS) score < 3, who had homocysteine levels greater than the 25th percentile ( > 9.5 umol/L for men; > 8.5 umol/L for women), and who were at least 75% compliant during the run-in, were eligible for this trial.

Exclusion Criteria
Women of childbearing potential, and persons whose strokes were due to an intracranial hemorrhage, dissection of a cervico-cephalic artery, veno-occlusive disease, drug abuse, or vasculitis, whose CT or MRI shows that a non-ischemic lesion caused the stroke syndrome, who had any of the following sources of cardiogenic emboli: prosthetic cardiac valve, intracardiac thrombus or neoplasm, atrial fibrillation, or valvular vegetation, who had any neurologic illness besides stroke that would confound evaluation of future strokes, who had any comorbid illness limiting life expectancy to < 2 years, who had severe congestive heart failure, renal insufficiency requiring dialysis, untreated B12 deficiency or pernicious anemia, or uncontrolled hypertension (systolic >185 mmHg or diastolic >105 mmHg on two readings separated by 5 min.), who had refractory depression, severe cognitive impairment, alcoholism, or other substance abuse, who had taken methotrexate, tamoxifen, L-dopa, phenytoin, or bile acid sequestrants that can decrease folate levels within the last 30 days, who took at baseline and were unwilling to discontinue multivitamins, folic acid, or single B6 supplements, who had any surgical procedure, invasive cardiac instrumentation, endarterectomy, stent placement, thrombectomy or other endovascular treatment of abnormal carotid artery performed or planned within 30 days of randomization, or who were participating in another clinical trial, were excluded from this study.