The demand for hemocompatibility is one of the fundamental requirements for a safe and sufficient application of artificial surfaces in contact with blood. Thrombus formation and infarctions of the capillary vascular system after blood-biomaterial interaction, as well as the activation of the complement system and the phenomenon of biodegradation, remain problematic areas. However, medical devices where large areas of artificial surfaces contact the blood of patients are applied in enormous quantities. In spite of the significance of this branch of modern medicine and some spectacular successes in therapy, organ support and organ replacement, clearly specified criteria and instructions for the design of devices and artificial blood-contacting surfaces do not yet exist. Standardized and generally-accepted test procedures for the precise quantification and validation of events at the blood-biomaterial interface are urgently needed: their absence limits safe medical therapy and the development of more efficient hemocompatible materials. This volume addresses the need for hemocompatibility standards by presenting the results of tests performed on the surfaces of the Reference Materials of the European Communities. Promoted by the EUROBIOMAT Research program of the European Communities in cooperation with the International Standards organization, this is a major contribution to the development of internationally accepted hemocompatibility test standards.