Recent studies have shown that hyperhomocysteinaemia is a common, independent and easily modifiable risk factor for atherosclerotic and thromboembolic diseases such as cerebrovascular disease, coronary artery disease and venous thrombosis. The vascular risk rises continuously across the spectrum of elevated plasma homocysteine concentrations. It is at least as important as cholesterol, lipoprotein abnormalities and hypertension and should be part of risk assessment, especially those at high risk. Moderately elevated plasma homocysteine concentration is readily correctable by folic acid, betaine, or vitamin B12 supplementation. It seems logical to assume that a reduction in homocysteine concentration will reduce the risk of ischaemic stroke, but there are as yet no published data to prove this. This review will discuss the aetiology and possible treatment of hyperhomocysteinaemia causing ischaemic stroke.