Background: Atherosclerotic lesions are heavily infiltrated by macrophages. Neopterin can be used as a marker of the activity of macrophages. Serum neopterin levels were elevated in non-renal patients with atherosclerosis. The intima-media thickness (IMT) of the carotid arteries in hemodialysis patients was significantly higher than in control subjects. In this study, we measured serum neopterin levels in hemodialysis patients and evaluated a possible correlation between neopterin levels and carotid IMT. Patients and Methods: Thirty-seven hemodialysis patients ( 26 male/11 female, mean age 47 +/- 15 years) and 12 healthy subjects ( 8 male/ 4 female, mean age 43 8 10 years) were included in this study. Serum neopterin levels were measured by using a commercial ELISA kit. Carotid IMT of the subjects were measured by high-resolution B-mode ultrasonography. Results: Carotid IMT values were 1.04 +/- 0.29 and 0.77 +/- 0.25 mm in hemodialysis patients and healthy controls, respectively ( p < 0.01). Serum neopterin levels were 110.9 +/- 19.1 and 3.8 +/- 2.3 ng/ml in hemodialysis patients and healthy controls, respectively ( p < 0.01). Serum neopterin levels were 103.2 +/- 21.3 ng/ml in hemodialysis patients with IMT < 1 mm ( n = 15), and 116.7 +/- 15.4 ng/ml in hemodialysis patients with IMT >= 1 mm ( n = 22) ( p < 0.05). Moreover, there was a significant correlation between serum neopterin levels and carotid IMT ( p < 0.05, r = 0.363). Conclusion: Our findings suggest that neopterin could be associated with the severity of carotid atherosclerosis in hemodialysis patients. Copyright (C) 2005 S. Karger AG, Basel.