Microbiologists are familiar with the concept that bacteria subjected to a sterilizing agent will, in theory, die exponentially with time at a uniform rate. Product inoculation involves artificially contaminating a sterile device with a known number of organisms, usually bacterial spores, and determining the number removed after exposure to the recovery method. Bioburden is the population of viable microorganisms on a raw material, a component of a finished device. The method of extraction most effective for bioburden recovery varies according to the substrate; therefore, individual products may require different extraction methods to optimize organism removal. Bioburden data should be trended by monitoring the number of organisms and the resistance to ensure control of the device materials and the manufacturing environment. The actual numbers of organisms recovered during testing may not represent the entire organism population actually on the device, but it is the resistance of the bioburden that must be known.