Vitamin D displays many extraosseous immunomodulatory effects. The aim of the study was to evaluate the level of vitamin D in patients with systemic sclerosis (SSc) and to analyze the associations between the concentration of the vitamin and clinical manifestations. In March-April 2009, 65 consecutive SSc patients underwent evaluation of vitamin D concentrations by the LIAISON immunoassay (normal 30-100 ng/ml). Serum levels between 10 and 30 ng/ml were classified as vitamin D insufficiency, while concentrations <10 ng/ml as vitamin D deficiency. None of the patients were receiving vitamin D supplementation at the time of or during the year prior to study entry. The mean level of vitamin D was 15.8 ± 9.1 ng/ml. Only three cases showed normal values; vitamin D insufficiency and deficiency were found in 43 and 19 cases, respectively. Patients with vitamin D deficiency showed longer disease duration (13.1 ± 6.8 versus 9.4 ± 5.5 years, P = 0.026), lower diffusing lung capacity for carbon monoxide (63.7 ± 12.4 versus 76.4 ± 20.2, P = 0.014), higher estimated pulmonary artery pressure (28.9 ± 9.9 versus 22.8 ± 10.4, P = 0.037) and higher values of ESR (40 ± 25 versus 23 ± 13 mm/h, P = 0.001) and of CRP (7 ± 7 and 4 ± 2 mg/l, P = 0.004) in comparison with patients with vitamin D insufficiency; moreover, late nailfold videocapillaroscopic pattern was more frequently found (52.6% versus 18.6%, P = 0.013). None of the patients showed evidence of overt mal-absorption. Low levels of vitamin D are very frequent in patients with SSc. Intestinal involvement is not likely the cause of vitamin D deficit; other factors such as skin hyperpigmentation and reduced sun exposition for psychological and social reasons may be implicated. Patients with vitamin D deficiency showed more severe disease in comparison with patients with vitamin D insufficiency, above all concerning lung involvement. Further trials are awaited to determine whether vitamin D could represent a modifiable factor able to interfere with SSc evolution.