Objective: A protective function of vitamin D in metabolic syndrome (MetS) has been described. The objective of the present study was to examine the relationship between serum 25-hydroxyvitamin D (25(OH)D) concentrations and MetS in non-diabetic systemic lupus erythematosus (SLE) women. Methods: Cross-sectional analyses of the relationship between concentrations of 25(OH)D, MetS, and its components were made in 160 non-diabetic SLE women. MetS was defined according to National Cholesterol Education Program Adult Treatment Panel III criteria. Serum 25(OH)D was measured by chemiluminescent immunoassay. Serum 25(OH)D concentrations were categorized into quartiles (