1.1 This guide describes methods for selecting test soils for cleaning validations based upon the characteristics of the soil, the physical characteristics of the device, and the clinical use of the device. 1.2 This guide describes the preparation and use of some test soils for the validation of cleaning instructions for reusable medical devices. 1.3 Reusable medical devices such as endoscopes, arthroscopic shavers, surgical instruments, and suction tubes are exposed to biological soils during clinical use. Preparation of these devices for reuse requires cleaning and disinfection and/or sterilization as applicable. Adequate cleaning is the first step in a process intended to prevent contaminant transfer to the next patient and medical practitioner. The soils, if inadequately removed, can interfere with disinfection and sterilization processes, as well as performance of the device. Acceptance criteria are based either on a visual assessment or quantitatively specified marker(s) endpoint(s) of the soil or both (ISO/TS 15883-5, Section 1). Endpoints after cleaning should be based upon possible interference with disinfection/ sterilization, risk to the patient or health care worker from the contaminant during further handling, and endpoints for cleaning established in the scientific literature. 1.4 The test soils are designed to simulate the contaminants that medical devices are likely to come in contact with during clinical use. The test soils discussed in this guide are a mixture of constituents that simulate what is commonly found in human secretions, blood, tissue, and bone fragments/shavings as well as non-patient derived soil (e.g., bone cement, lubricants, and dyes) during clinical procedures. The test soils also simulate the physical parameters (e.g., viscosity, adhesion) of clinical material to which the medical devices will be exposed.