The study of absorption, distribution, metabolism and elimination profiles of drugs as a quantitative discipline has developed from a purely development focus in the 1980s to a truly predictive quantitative discovery and development discipline that is having a significant impact on reducing development attrition. This chapter will focus on a â handfulâ of mathematical and physiological principles that have underpinned this transformation. It will also illustrate how our growing understanding of the relationship between compound physical properties, efficacy, pharmacokinetics, metabolism and safety is driving a predictive paradigm which can link compound design all the way through to human exposure and safety.