Homeostasis is mediated through interactions of adhesion molecules on the surface of platelets which belong into the families of selectins, integrins and immunoglobulins with soluble plasma proteins, surface molecules of activated endothelial cells and molecules of extracellular matrix. The membrane expression of some adhesion molecules (P-selectin) which are the part of granular system of resting platelet identify activated platelet. Adhesion molecules of platelets could be detected by immunochemistry through flow cytometry. By this approach the inherited defects of adhesion molecules on platelets and the activated platelet could be detected. The detection of activated platelets is very useful in many clinical conditions.