The objective of this study was to determine the vitamin D status and its relationship with disease and therapy features and with bone mineral density in women with systemic lupus erythematosus. Non-pregnant systemic lupus erythematosus women with dual-energy X-ray absorptiometry and vitamin D measurements performed between May 1 2005 and August 31 2006 were studied. In each patient, the lowest T-score of the first dual-energy X-ray absorptiometry scan during the study period was used. In postmenopausal women, a T-score > or = 1.0 standard deviation was considered normal, between -1.0 and -2.5 standard deviations osteopenia and < or = 2.5 standard deviations osteoporosis; in premenopausal women a T-score > or = 2.5 standard deviations was normal and < or = 2.5 standard deviations defined as reduced bone density. 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels were determined at the time of dual-energy X-ray absorptiometry. A 25-hydroxyvitamin D level of <80 nmol/L was defined as sub-optimal and a level <40 nmol/L as deficient. Demographic and clinical variables were investigated for association with vitamin D levels by univariate and multivariate analyses. One-hundred and twenty-four systemic lupus erythematosus women had dual-energy X-ray absorptiometry scans and vitamin D assays performed during the study period. Sub-optimal 25-hydroxyvitamin D levels were found in 82 (66.7%) and deficient 25-hydroxyvitamin D levels in 22 (17.9%) patients. The disease-related features examined at the time of vitamin D assays or bone mineral density showed no correlation with vitamin D levels by univariate analyses. Neither 25-hydroxyvitamin D nor 1,25-dihydroxyvitamin D was associated with bone mineral density status among these patients. A multivariate logistic regression model identified season, cumulative glucocorticoid exposure, and serum creatinine as being associated with 25-hydroxyvitamin D levels, whereas ethnicity, glucocorticoid exposure, and serum creatinine were associated with 1,25-dihydroxyvitamin D levels. In conclusion, sub-optimal vitamin D status is common in women with systemic lupus erythematosus and is related to season, cumulative glucocorticoid dose, and serum creatinine.