Growing knowledge about gene-disease associations will lead to new opportunities for genetic testing. Many experts predict that genetic testing will become increasingly important as a guide to prevention, clinical management, and drug treatment based on genetic susceptibilities. As part of a Human Genetic Epidemiology workshop convened by the Centers for Disease Control and Prevention, a group of experts evaluated the evidence needed when considering the appropriate use of new genetic tests. Because new tests are likely to vary in their predictive value, their potential to direct prevention or treatment efforts, and their personal and social consequences, the task of determining appropriate use will require careful consideration of a variety of factors, including the analytic validity, clinical validity, clinical utility, and ethical, legal, and social implications of the test. Standardized formats are needed to summarize what is known and not known about new genetic tests with respect to each of these features. Following criteria for the objective assessment of test properties, reports should be structured to enable policy makers, clinicians, and the public to identify the available evidence, so that uncertainties can be taken into account when considering test use and planning future research.