Background Total serum sialic acid concentration has been reported to predict death from cardiovascular disease. This study was performed to assess the relation between serum sialic acid concentration and the angiographic extent and severity of coronary atheroma in patients with stable angina. Methods Quantitative coronary angiography was performed in 40 patients with stable angina with either triple-vessel disease (23 patients) or normal/nearly normal coronary arteries (17 patients). A colorimetric assay for the enzymatic determination of serum sialic acid was used. Results Serum sialic acid concentration was not significantly different in patients with normal or nearly normal coronary angiograms compared with those with triple-vessel disease (68 ± 10 mg/100 mL and 68 ± 11 mg/100 mL, respectively). Neither was there any association between the extent or severity of coronary disease and serum sialic acid levels. Conclusions Serum sialic acid concentration does not appear to be associated with the extent or severity of coronary artery disease in patients with stable angina pectoris. Thus the previously described association between serum sialic acid and cardiovascular death may reflect the role of mechanisms other than the severity of coronary artery narrowings. (Am Heart J 1998;136:620-3.)