In recognition of the earlier experiences with genetic diagnostic services and in anticipation of a greater potential for genetic testing for presymptomatic disease and disease susceptibility, this article provides an analysis of policy development for cystic fibrosis carrier screening. The deficiencies of relying on an extemporaneous model for health policy development are described. Preferably, an evidentiary model, based on the evaluation of clinical research and incorporating professional and public attention to underlying normative issues, should define the standard of care. Appropriate procedural mechanisms should be established at both state and federal levels to prevent the unnecessary confusion, expense, and personal or social harms likely to result from a completely unrestrained application of developing genetic technologies or continuing ad hoc responses to rapid increases in genetic diagnostic capabilities. A broadly constituted national advisory commission on the ethical, legal, and social implications of the Human Genome Project would provide an important locus for national decision making and may offer an efficient mechanism for implementing the evidentiary model, promoting public involvement at a time when social policy decisions must be made to restructure the health care system to be more sensitive to issues of access, allocation, and costs.