Performing Quantitative Microbiological Risk Assessment (QMRA) during food processing requires mathematical models and probability functions to describe the propagation of microorganisms from the raw materials to the consumer’s plate. Estimating quantitatively the risk (broad sense of “risk”, i.e. risk for the consumer but also risk of having a concentration higher than a target such as a Food Safety Objective or a Performance Objective) provides flexibility in comparing the efficiency of different risk reduction measures, which could be potentially implemented at the operational level, by predicting their effect on the model output. The present Chapter is focused on the development, implementation and the interpretation of QMEA models applied to food processing. Thermal inactivation, partitioning and growth are the three steps detailed through examples and exercises. The interpretation of results is done through sensitivity and scenario analysis. The exercises are provided at the end of section Risk Analysis. They have to be carried out within Excel using the Add-In program @Risk. The Excel sheets are available in the attached USB stick.