As we identify genes predictive of diseases such as heart disease, stroke, or cancer, we may unwittingly deprive individuals and families at risk of such diseases from access to health care. This is a problem in distributive justice. Commercial health insurance is built along lines similar to other forms of commercial insurance in which the notion of "actuarial fairness" plays a key role. Actuarial fairness contends that parties seeking insurance ought to pay according to their respective risks of filing a claim. Underwriting is the process by which insurers estimate the likelihood that an applicant would be making a claim. The human genome project has brought the latent ethical problems in commercial health insurance to the surface. In the scenario feared by insurers, predictive genetic tests will filter into general medical practice. Individuals who learn that they are at increased risk of such disease are more likely to purchase insurance. Such behavior is known as "adverse selection" by the insurance industry. Individual companies, in an effort to avoid adverse selection, may seek genetic information about their prospective customers, and other companies may follow suit. Such a scenario has led to the establishment of a national Task Force on Genetic Information and Insurance under the aegis of the human genome project. The Task Force seeks to clarify the empirical and moral components of the controversy. Key questions include the social purpose of health insurance, whether adverse selection is a genuine concern in the context of genetic testing, and the appropriateness of risk underwriting for access to health care.(ABSTRACT TRUNCATED AT 250 WORDS)