This part of ISO 10993 provides general requirements for evaluating the interactions of medical devices with blood. It describes a) a classification of medical and dental devices that are intended for use in contact with blood, based on the intended use and duration of contact as defined in ISO 10993-1, b) the fundamental principles governing the evaluation of the interaction of devices with blood, c) the rationale for structured selection of tests according to specific categories, together with the principles and scientific basis of these tests. Detailed requirements for testing cannot be specified because of limitations in the knowledge and precision of tests for interactions of devices with blood. This part of ISO 10993 describes biological evaluation in general terms and may not necessarily provide sufficient guidance for test methods for a specific device.