Pharmacogenomics holds much promise for the application of genetic information to the improvement of clinical care. Ethical issues for pharmacogenomics arise at the intersection of the spheres of drug development and genetic testing. Clinical drug trial designs which use subject selection based on genotype must consider the features of scientific validity, social value and risk-benefit ratio, and later, the impact of this strategy on post-market studies and clinical use of drugs. Although the testing context for pharmacogenomic tests is different from other genetic tests, decisions to use any new clinical tests in medical practice will require evaluation of not only the benefit linked to improved drug use but also the risks arising in part from the scale of testing, predictive value and collateral potential of the genetic test. Integration of pharmacogenomic information into clinical practice will require clinical trials to assess their clinical usefulness, including the impact of tests on therapeutic outcomes. Trials will also be needed to demonstrate the effectiveness of education, informed consent and counseling.