Over the past decade, medical genetics has emergedas an important and powerful medical specialty with increasing appreciation of its role and function among the medical specialties. This emergence is related to a great extent to the progress in the Human Genome Project which promises wide-ranging applications in the diagnosis, treatment and prevention of human diseases [Hoffman, 1994]. Nevertheless, discussions about the role of genetics in preventive medicine and public health rightfully lead to ethical, legal and social concerns about general applicability of genetic testing in the population [Garver, 1994; Holtzman, 1989]. The interpretation of the word prevention in the context of genetic diseases leads to the unavoidable discussions of genetic engineering, prenatal diagnosis and selective termination, as well as broader concerns about discrimination in health care coverage, employment and in society. Figure 1 shows the classical public health view of disease prevention when applied to infectious and environmental agents. Primary prevention is classically thought of as the interruption of transmission of infectious agents or avoidance of exposure to environmental agents in the population through education, behavior modification, immunizations, and environmental measures (e.g., human immunodeficiency virus [HIV] infection or cigarette smoking). Secondary prevention is thought of as the interruption of clinical disease after the acquisition of the infectious agent or exposure to the environmental agent. In the case of HIV, this entails steps to prevent or delay the onset of the acquired immunodeficiency syndrome (AIDS) by using drugs and other medical, nutritional and psychosocial measures. Tertiary prevention is thought of as the prevention of complications of the disease after it occurs [Khoury et al., 1996]. For example, this applies to the prevention of opportunistic infections (OI) in AIDS through appropriate prophylactic medical guidelines.