Pharmacokinetics involves the study of how a drug moves across the body with time, and various parameters are used to describe this process of drug disposition. An understanding of these pharmacokinetic parameters is essential in the optimization of drug therapy. Clinical pharmacokinetics particularly deals with the factors responsible for the inter-individual variations in the kinetics of drugs. At a fundamental level, it is important to appreciate the differences between zero-order and first-order elimination kinetics. Further, pharmacokinetic analytical methods are available that help us to appreciate the relation between various parameters and thereby enable us to understand, predict and optimize the drug kinetics. These analytical methods primarily include compartmental modelling, non-compartmental analysis and physiologically based pharmacokinetic modelling. They fundamentally differ in their assumptions and are preferentially used in different contexts based on their advantages. While the above-mentioned methods are described at an individual level, population pharmacokinetics studies summarize the kinetic parameters at a population level. In addition to the understanding of pharmacokinetic principles, the availability of therapeutic drug monitoring services plays a major role in optimizing the day-to-day clinical management of patients on drugs with narrow therapeutic index.