This article provides an introduction to the fundamental principles of pharmacokinetics (PK) and pharmacodynamics (PD) as they apply to understanding the application of pharmacogenetics (PGx) in a clinical setting. PGx establishes connections between the disciplines of pharmacology and genetics. As such, one functional component of PGx involves establishing relationships between phenotypes and genotypes with respect to predicting the response of medications in individual patients. The article begins by describing each of the concepts, followed by discussing the clinical utility of PGx and pharmacodynamics in a laboratory medicine setting; it then makes a link with the evolving field of PGx from the perspective of clinical laboratory medicine. Laboratory medicine serves as a catalyst for transitioning PGx into clinical settings, and as such, the article concludes by describing the future role of clinical laboratories in the application of PGx to patient care.