For many decades cardiovascular and thrombotic diseases have been one of the major causes of death worldwide and also research on this issue has become more and more important. In order to fully comprehend the phenomenon of thrombotic diseases one has to concentrate on hemostasis and its complex procedures. The molecular mechanisms of this type of bleeding control have been thoroughly researched and many patients have already benefitted from this knowledge. However, the interaction between platelets, which are jointly responsible for hemostasis, and leucocytes is a relatively new discovery. Platelets are not only able to perform hemostatic but also immunomodulatory tasks. The aim of this thesis is to find out whether different stimuli of variable intensity make platelets take effect thrombotically or immunomodulatory. Moreover, this thesis deals with the impact that lipopolysaccharides have on cells and tries to find out whether the presence of lipopolysaccharides modulates stimuli. For this purpose, stimulation experiments on human whole blood with the antagonists ADP, CVX and Trap6 were performed. Measurements by means of flow cytometry with the focus on CD61-, CD11b- and p-selectin-expression were also carried out. Besides, aggregometric measurements were performed under the very same stimulation conditions. Finally, one comes to the conclusion that the weak thrombotic antagonist ADP (in contrast to the stronger antagonists CVX and Trap6) was significantly more effective with regard to immunomodulation.