This part of ISO 10993 describes a) the general principles governing the biological evaluation of medical devices; b) the categorization of devices based on the nature and duration of their contact with the body; c) the selection of appropriate tests. This part of ISO 10993 does not cover testing of materials and devices that do not come into direct or indirect contact with the patient's body, nor does it cover biological hazards arising from any mechanical failure. NOTE Other parts of ISO 10993 cover specific tests (see also the rationale in A.2).