diabetic nephropathy and macro- vascular complications. Thus it is possible to conBackground: Type 2 diabetes is associated with increased blood concentrations of acute phase reactants including; sialic acid, ai-acid glycoprotein, serum amyloid A, and the main cytokine mediator of acute phase response, interleukin-6. Through the action of cytokines on many tissues, acute phase response could be a major contributor of biochemical and clinical features of metabolic syndrome X and type 2 DM. We investigated whether sialic acid, CRP, and TNF-a levels were elevated in type 2 diabetic patients who had features of syndrome X and whether they were correlated with diabetic vascular complications. Methods: Group 1 was type 2 diabetic patients with any of 4 or 5 features of syndrome X (n=24). Group 2 was type 2 diabetic patients with 0 or 1 features of syndrome X (n=29), and group 3 was healthy nondiabetic control subjects (n=19). We compared the levels of sialic acid, CRP, and TNF-a in group 1, 2 and 3. We also observed the relationship between sialic acid, CRP, TNF-a levels and diabetic micro, macrovascular complications and studied the correlation between these markers and components of syndrome X. Results: Group 1 had significantly higher sialic acid levels than group 2 (68.3+19 vs. 59.9+9.7 mg/dL, p=0.047). But the CRP, and TNF-a levels were similar in three groups. Serum sialic acid levels were signifieantly higher in proteinuria group than in normo- and microalbuminuria groups (81+27.6 vs. 59.9+7.1, 61.2+7.9 mg/dL, p=0.001, 0.005). Serum CRP levels were also higher in proteinuria groups (32.9+59.8 vs. 6.4+1.9, 6.0+3.1mg/L, p=0.017, p=0.037). Serum sialic acid levels were significantly higher in the macrovascular complication group (70.5 +21.3 vs. 60.5+ 6.8 mg/dL, p=0.015). Levels of sialic acid were correlated with urinary albumin excretion rate, log triglyceride, CRP, and fasting C-peptide. Levels of CRP were correlated with sialic acid and fasting C-peptide. Conclusion: Serum sialic acid levels were significantly elevated in type 2 diabetic patients who had features of syndrome X, and were also elevated in patients with si- der that the mechanisms involved in the acute phase response can contribute to the pathophysiology of type 2 diabetes and syndrome X. Vascular complica- tions do further increase stress reactions in type 2 diabetes.