[unreadable] Kidney disease can have a substantial and pervasive negative effect on quality of life, both by way of direct effects of the disease and by way of its treatment and comorbid conditions. Homocysteinemia, or abnormally high levels of total plasma homocysteine (tHcy), is highly prevalent in patients with kidney disease, and has been shown to be an independent risk factor for cardiovascular disease. There also appear to be links between homocysteinemia and impaired cognition. Cognitive impairment is an under-recognized and inadequately understood comorbid condition in renal patients. Homocysteinemia can be reduced by vitamin therapy. Whether such therapy results in sustainable improvement in cognition in renal patients has not been previously examined, and is the focus of our proposed study. We will test the following hypotheses: 1) tHcy reduction via therapy with vitamins B6, B12, and folate will result in better cognitive outcomes in patients with chronic renal failure (CRF) or end stage renal disease (ESRD), compared with patients treated with placebo; and 2) Patients on vitamin therapy will exhibit a smaller 1-year decline in cognition, compared with those on placebo. This study will be conducted at the Boston and Palo Alto VA Medical Centers on renal patients already enrolled in the ongoing VA-funded Homocysteine Study (HOST), which is a national randomized, double-blind, placebo control, phase III clinical trial of tHcy reduction via multivitamin therapy. We will administer a short cognitive assessment battery by telephone to up to 726 renal patients, and will subsequently readminister the battery one year later to assess the rate of cognitive decline in the treatment and placebo groups. Determining whether the cognitive effects of kidney disease and associated comorbidities are moderated by tHcy and B vitamin levels would improve quality of life and reduce the rates of cognitive impairment and dementia in renal patients [unreadable] [unreadable]