Sterilization validation is so often considered to attain SAL (Sterility Assurance Level) of 10 -6 , but this is not correct. The correct is to attain both simultaneously SAL of 10 -6 and material and functional compatibility of the sterilized devices. SAL of 10 -6 can be easily attained by using BI (Biological indicator) and D (decimal reduction value). For example it is 12D as an overkill method. On the contrary, it is quite hard to attain material and functional compatibility to the products exposed up to SAL of 10 -6 . One typical example is the sterilization of endoscope. Endoscope is repeatedly used after sterilization, but the endoscope part to carry out biopsy is deteriorated after a few times use. So, sterilization is not conducted and HClO (pH 4-6) or only water washing is so often conducted in the exact healthcare facilities. By these methods purion, hepatitis virus or H. pylori is infected between human to human during endoscope inspection. Most easy method for sterilization of endoscope is gamma-ray irradiation.