OBJECTIVE--To examine the association between serum sialic acid concentrations and coronary heart disease (CHD) in a cross-sectional study of non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS--NIDDM patients (n = 145) attending a diabetic clinic were studied. CHD status was assessed by questionnaire and electrocardiogram coding, and potential risk factor assessment included measurement of fasting serum lipid and lipoprotein concentrations, blood pressure, and urinary albumin excretion rate (AER). RESULTS--Male NIDDM patients with CHD had a higher serum sialic acid level than those without CHD: 2.56 (2.24, 2.72) mmol/l vs. 2.24 (2.18, 2.30) mmol/l, P = 0.01, mean (95% confidence interval). They were also older, had a longer duration of diabetes, had a higher AER, had higher total triglyceride, very-low-density lipoprotein triglyceride and cholesterol, and lipoprotein(a) concentrations, and had a lower apolipoprotein A1 concentration. In an age adjusted multiple lipoprotein(a), hypercholesterolemia, and hypertension were associated with CHD. In women, only hypertension treatment was associated with CHD. CONCLUSIONS--There is a strong univariate association between elevated serum sialic acid and CHD in men (but not women) with NIDDM.