BACKGROUND: The aim of this study was to evaluate the possible role of NF- B activation and AP-1 by oxidative stress in atherosclerosis in diabetic patients by measuring the carotid intima-media thickness, intracellular ROS generation and activation of transcription factors, including nuclear factor-kappa B (NF- B) and activator protein-1 (AP-1). METHODS: Sixty-six patients (28 males, 38 females; age 56.1 13.4 years; duration of diabetes 115.7 83.4 months) with type 2 diabetes mellitus (DM) were selected for this study. The DM patients included in this study were divided into those with a normal carotid intima-media thickness (Group II) and those with an increased intima-media thickness (Group III). 57 healthy controls matched for age and sex with the DM patients (Group I) were randomly selected. Dichlorodifluorescein (DCF)-sensitive intracellular ROS was measured by fluorescent spectrometry. The activities of NF- B and AP-1 in PBMCs were measured by an electrophoretic mobility shift assay. RESULTS: No differences were evident between the groups in terms of gender, age, BMI, blood pressure, total cholesterol, triglyceride, LDL-cholesterol and HDL-cholesterol. Spontaneous and H2O2 (or phorbol-12-myristate-13-acetate, PMA) stimulated ROS were significantly higher in the PBMCs from the DM patients with an increased intima-media thickness (Group III) than in those without (Group II), and were also higher in the control group (Group I). Moreover, the activities of NF- B and AP-1 were significantly higher in Group III than in Groups I or II. CONCLUSION: The present study demonstrates that intracellular ROS generation, and NF- B and AP-1 activation in PBMCs strongly correlates with the carotid artery IMT. These clinical results suggest that increased oxidative stress in PBMCs may play a role in the pathogenesis of atherosclerosis in DM patients .