This chapter is intended as a means of introducing dose response models and modeling to the novice quantitative microbial risk assessment (QMRA) modeler. The concept of and derivation of the models is outlined so the user understands the underlying limitations of the models and data. The chapter highlights the appropriate use of the dose response models and their uncertainty estimates and the inclusion of environmental exposure uncertainty into the QMRA to again control for uncertainties in the dose response models. In QMRA the dose response assessment is the yardstick of risk, essentially inserting the vital quantitative risk estimation into QMRA. The first of the advanced mechanistic dose response models is based on host age. Based on the framework developed for age dependency, time post inoculation advanced dose response models, essentially develop a time line of likely impacts based on the amount of time it has been since the host organism has been dosed.