Objective To evaluate the association between serum 25-hydroxyvitamin D3 [25 (OH) D3],parathyroid hormone,and arterial stiffness in patients with type 2 diabetes.Methods Serum 25 (OH) D3 and parathyroid hormone(PTH) were determined in a cross-sectional sample of 258 patients aged 30 years and over.Arterial stiffness was assessed by pulse wave velocity(PWV) obtained with a VP-1000 pulse wave unit.Fasting plasma HbA1c,lipid profile,calcium,and high sensitive-C reactive protein were determined.Results (1)The prevalence of vitamin D3 deficiency was high(79.84％) in patients with type 2 diabetes.(2) Those with lowered serum vitamin D3 levels had raised PWV [(1610.76 ± 142.70 vs 1527.95 ± 58.02) cm/s,P＜0.05].(3) Multiple stepwise regression analysis showed that 25 (OH) D3 was an impact factor of PWV risk score,which was independent of age,duration of diabetes,and systolic blood pressure(β =-0.256,P＜0.01).(4) Serum PTH was positively correlated with PWV (r =0.210,P ＜ 0.05) and systolic blood pressure (r =0.229,P ＜ 0.05),but negatively correlated with 25 (OH) D3 (r =-0.153,P ＜ 0.05).Conclusions 25 (OH) D3 deficiency is common in patients with type 2diabetes,and a low serum 25 (OH) D3 level is significantly associated with increased arterial stiffness in these patients.The association of serum PTH with arterial stiffness may result via changes in vitamin D and blood pressure.