Background and aim: Systemic lupus erythematousus (SLE) is a autoimmune disease that cause frequent vascular complication even in young patients without atherosclerotic risk factors. However, it is not determined whether autoimmune inflammatory response causes endothelial dysfunction and atherosclerosis or not. Therefore, we evaluated the endothelial function and atherosclerosis in young patients with SLE. Methods: Using high frequency(15MHz) linear array transducer, flow mediated dilation(FMD) was assessed in the brachial artery by measuring the change in brachial artery diameter in response to hyperemic flow. Intima-media thickness(IMT) of the common carotid artery was also measured. We compared 16 young female SLE patients(mean age:29.7짹13.2 years) with 10 female young controls(mean age:26.4짹0.8 years). In all SLE patients, SLE disease activity index(SLEDAI) score was calculated with 15 clinical manifestations and 9 laboratory markers. Results: 1. % FMD was decreased in SLE than that of controls(5.16짹4.4% vs 10.1짹1.5%, p<0.05). 2. %FMD was closely related to SLEDAI score in SLE(r=-0.6, p<0.05). 3. IMT was increased in SLE than that of controls(0.52짹0.17mm, 0.21-0.79mm vs 0.36짹0.03mm, 0.32-040 mm, p<0.05). 4. % FMD was not related to IMT in SLE (p=NS). Conclusion: It suggests that autoimmune inflammatory response associated with SLE cause endothelial dysfunction and atherosclerosis even in young age without overt cardiovascular risk factors and endothelial dysfunction is closely related to the disease activity.