['Patients with chronic kidney disease (CKD) not requiring dialysis have a high prevalence of 25-hydroxyvitamin D (25(OH)D) deficiency but the relationship between 25(OH)D levels and metabolic syndrome is unknown in this population.', 'This study analyzed stored plasma samples from 495 non-diabetic subjects with severe kidney disease, not yet on dialysis, who participated in the homocysteine in kidney and end stage renal disease study. Metabolic syndrome was defined as the presence of all three of the following: (1) Serum triglycerides ≥ 150 mg/dl or drug treatment for hypertriglyceridemia; (2) serum high density lipoprotein-cholesterol (HDL-C) < 50 mg/dl for women or < 40 mg/dl for men or drug treatment for dyslipidemia; and (3) blood pressure ≥ 130/85 mmHg or drug treatment for hypertension. Multivariate logistic regression models were used to evaluate the cross-sectional association between plasma 25(OH)D levels and metabolic syndrome.', 'The prevalence of metabolic syndrome increased as 25(OH)D levels declined, with the highest prevalence in participants with 25(OH)D levels < 20 ng/ ml. Participants with 25(OH)D levels < 20 ng/ml had a significantly increased risk of metabolic syndrome compared to subjects with levels > 30 ng/ml after adjustment for multiple confounders (OR 2.25, 95% CI 1.25 - 4.07). Plasma 25(OH)D levels were inversely associated with diastolic blood pressure (R = -0.10, p = 0.029) and serum triglyceride levels (R = -0.14, p = 0.002).'] Is 25-hydroxyvitamin D deficiency associated with an increased risk of metabolic syndrome in patients with non-diabetic chronic kidney disease?