We have elaborated a system for testing the phagocytic activity of human blood platelets. Blood was sampled to heparin and ACD and centrifuged. This procedure yields platelet rich plasma (PRP). As a substrate for phagocytosis we used Staphylococcus aureus 209P. The ratio of platelets to bacteria is 1:1. Incubation of bacteria and platelets continued up to 10 minutes. Lysostaphine was introduced to the phagocytic system to destroy all bacteria outside the blood platelets. The maximal values for the percentage of phagocytizing blood platelets were 0.7% and the phagocytosis index of 1.0 was reached at 6 minutes with incubation of bacteria and platelets. The authors pay attention to the role of blood platelets in antibacterial mechanisms.