Book excerpt: The study of pharmacogenetics and pharmacogenomics focuses on how our genes and complex gene systems influence our response to drugs. Recent progress in clinical therapeutics has led to the discovery of new biomarkers that make it technically easier to identify groups of patients which are more or less likely to respond to individual therapies. The aim is to improve personalised medicine - not simply to prescribe the right medicine, but to deliver the right drug at the right dose at the right time. This textbook brings together leading experts to discuss the latest information on how human genetics impacts drug response phenotypes. It presents not only the basic principles of pharmacogenetics, but also clinically valuable examples that cover a broad range of specialties and therapeutic areas. This textbook is an invaluable introduction to pharmacogenetics and pharmacogenomics for health care professionals, medical students, pharmacy students, graduate students and researchers in the biosciences.