Diseases of the central nervous system are found in patients with severe hyperhomocysteinemia (HHcy). Epidemiological studies show a positive, dose-dependent relationship between mild-to-moderate increases in plasma total homocysteine concentrations (Hcy) and the risk of neurodegenerative diseases, such as Alzheimer's disease, vascular dementia, cognitive impairment or stroke. HHcy is a surrogate marker for B vitamin deficiency (folate, B12, B6) and a neurotoxic agent. The concept of improving the patient's clinical outcome by lowering of Hcy with B vitamins seems to be attractive. Recent B vitamin supplementation trials demonstrated a slowing of brain atrophy and improvement in some domains of cognitive function. Meta-analysis of secondary prevention trials showed that B vitamins supplementation caused a decrease in plasma Hcy and a trend for lowering the risk of stroke. HHcy is common in elderly people. Therefore, it seems prudent to identify B vitamin deficient subjects and to ensure sufficient vitamin intake. Therefore, recent evidence supports the role of Hcy as a potential biomarker in age-related neurodegenerative diseases.