objective: Markers of platelet activation are elevated in coronary artery disease. We sought to identify the presence and the potential associations of different markers of platelet activation. Methods:We studied patients with unstable angina (n=28), patients with stable angina (n=36) and patients without coronary artery disease (n=30); sex and age matched. Blood levels of the adhesion molecule P-selectin, Thromboxane B2 and Serotonin were measured by enzyme immunoassays.results: When we compared the groups the results were: sP-selectin, thromboxane B2 and serotonin levels were significantly higher in patients with unstable angina than in patients with stable angina.conclusion: These markers of platelet activation were able to identify unstable forms of coronary artery disease.