According to the International Organization for Standardization (ISO), a biological indicator is a test system containing viable microorganisms providing a defined resistance to a specified sterilization process. Biological Indicators (BIs) have been in use for several decades and are used in hospitals, food processing, tattoo parlors, dentist offices, pharmaceutical and medical device manufacturing, ambulatory surgical centers and anywhere else where validation and verification of an adequate sterilization cycle is required. BIs come in many different shapes, sizes and configurations. Spore Strips have been in use for several decades and are still very widely used for a variety of sterilization processes. Self-Contained Biological Indicators (SCBIs) have become much more popular over the past 30 years, as they are more user friendly and often offer reduced incubation times. For situations where typical BIs are not appropriate, suspensions are widely used to directly inoculate product/substances and Mesa’s line of industrial use BIs are available to test the lethality of a sterilization cycle in a very specific area of a product or load.