This chapter discusses sterilisation which is defined as the process by which various surfaces and articles are freed of all living microorganisms including their spores. Antiseptics are sterilising agents which have antimicrobial activity and can safely be applied to living tissue. High level disinfection procedure kills all organisms with the exception of bacterial spores and certain viruses. Sterility assurance level is probability of survival of microorganisms after a terminal sterilisation process and a predictor of the efficacy of the process. The first and most important step in decontamination is thorough cleaning and rinsing. If an article is not clean, retained soil could inactivate chemical germicides or protect microorganisms from destruction during sterilisation. Advantages include speed, good penetration, economy, ease of use, absence of toxic products or residues, and reliability. Chemical sterilisation is done by liquid chemical agents and is especially useful for heat sensitive equipment. Radiation sterilisation is the dominant process for sterilising disposable products by manufactures. Gammaradiation is mainly used.