Pharmacogenetics is a rapidly evolving field that will undoubtedly lead to the development of pharmacogenetic tests. Such tests will need to be assimilated into healthcare systems, but represent a further call on scarce healthcare resources. Therefore, in order for a pharmacogenetic test to fulfill its potential beyond the laboratory and into the clinical environment, it must prove itself on a wide range of multifaceted criteria. The test must have proven and reproducible analytical and clinical validity, and stand up to critical appraisal of clinical utility and cost–effectiveness. Pharmacogenetic testing can be considered to be a form of screening, and the experience that has been gained to date in evaluating other forms of screening tests may prove beneficial in evaluating pharmacogenetic technology. It is essential that the goals of pharmacogenetic testing are defined as early as possible to ensure that appropriate studies can be designed to provide the evidence base, and thereby enable appropriate evaluation of the technology by clinicians and healthcare administrators for incorporation into clinical practice. This review focuses on issues that will need to be considered in the scientific assessment of pharmacogenetic testing.