According to AAMI, the FDA, CDC, CEN, Health Canada, CSA, and other regulatory agencies around the globe, validation of medical device cleaning, disinfection and sterilization should be done with test soils that are modeled on the residuals the medical device is likely to be contaminated with during actual clinical use. ATS (Artificial Test Soil) is just such a soil. The ATS formulation is based upon experimental data representing the "worst case" soil level from patient-used medical devices and therefore represents a standardized soil formulation that is applicable to simulated-use testing of a wide range of medical device. ATS is composed of protein, carbohydrate, hemoglobin and optionally endotoxins, in proportion to the worst-case levels found in patient-used surgical instruments. Further, ATS can be inoculated with microbiological markers for challenging sterilization and disinfection.