OBJECTIVE : Blood pressure (BP) physiologically declines more than 10% at night. Subjects who do not experience this drop are classified as non-dippers. They have a higher risk of cardiovascular diseases (CVD). Vitamin D deficiency and non-dipper pattern have been associated in the general population. Patients with systemic lupus erythematosus (SLE) are more likely to have vitamin D deficiency, a non-dipper pattern and CVD. We aimed to evaluate a possible relationship between vitamin D deficiency and non-dipper pattern in patients with SLE. METHODS : Using 24-hour ambulatory BP monitoring, 77 women with SLE were divided into dippers and non-dippers. 25-hydroxyvitamin D (25(OH)D) levels were compared between both groups. A multivariate analysis was used to determine which variables were independently associated with non-dipper pattern. RESULTS : 62% of patients were non-dippers. They had lower levels of 25(OH)D than dippers (19.4±8.9 vs. 25.9±10.1 ng/ml, p=0.005). Patients with lower 25(OH)D levels were more likely to be non-dippers (OR 3.7, 95%CI 1.2-11.4; p=0.025). The nocturnal decline of mean BP correlated with levels of 25(OH)D (r=0.227, p=0.047). Night-time systolic, diastolic and mean BP inversely correlated with the levels of 25(OH)D (r=-0.274, p=0.016; r=-0.238, p=0.037, and r=-0.260, p=0.022, respectively), but only night- time systolic BP remained significant after adjustment for age and body mass index (r=-0.228, p=0.049). 25(OH)D levels and the use of mycophenolate were found to be independently associated with non-dipper pattern in SLE patients. CONCLUSIONS : Vitamin D deficiency may contribute to the development of a non-dipper pattern in patients with SLE.