The role of endothelial dysfunction and platelet activation in patients with cardiac syndrome X is controversial. The aim of this study was to investigate the plasma levels of circulating E- and P-selectin molecules in patients with syndrome X. The study included 21 patients with cardiac syndrome X (11 men and 10 women, mean age = 56 +/- 5 years) and 20 patients with significant coronary artery disease who had stable angina pectoris (11 men and 9 women, mean age = 60 +/- 8 years). Twenty-two age- and sex-matched subjects (12 men and 10 women, mean age = 58 +/- 8 years) undergoing diagnosis of atypical chest pain in whom coronary arteries were found normal and exercise test had no signs of ischemia served as the control group. Syndrome X was defined as presence of typical chest pain on exertion or at rest with positive exercise test and angiographically normal epicardial coronary arteries with no evidence of coronary spasm after intracoronary infusion of ergonovine maleate. The mean plasma concentrations of P-selectin were significantly elevated both in patients with coronary artery disease and syndrome X as compared with control subjects (49.15 +/-7.47 and 42.80 +/- 8.93 vs 22.63 +/-6.47 ng/mL, p < 0.001). Similarly, both patients with coronary artery disease and syndrome X had higher plasma concentrations of E-selectin than the control group (78.85 +/- 16.69 and 68.38 +/- 15.30 vs 36.43 +/- 4.72 ng/mL, p < 0.001). In conclusion, patients with syndrome X had increased plasma concentrations of soluble adhesion molecules, E-selectin and P-selectin, reflecting an ongoing chronic inflammation involved with endothelial dysfunction and enhanced platelet activation/damage in this setting.