Because of the peculiar history of how the US government has viewed health care as a market good, a commodity to be bought and sold, health policy formation in the United States is driven, not by reactions to problems as defined by rational federal health policy analysts and process, but by situations and forces occurring outside the health policy arena. Therefore, health policy debates and outcomes are a function of the impact of various external factors as opposed to the specific health care needs of the population. Factors that externally affect health policy formation are industrialization, labor issues, and the employee/employer relationship. Other factors include the introduction and subsequent increases in individual and corporate taxation and the ever-expanding influence of the health care givers industry. Thus, national health policy outcomes are determined by what is done in other realms. Using problem definition as an analytical tool, key questions to be addressed include: How were different policy proposals affected by other realms than public health policy? By whom? Through what means? For what purposes? With what effects on the policymaking process and outcome? An inductive, exploratory case study of the following specific legislative debates and their respective content using problem definition will be used to synthesize the role and impact of external forces on the formation of national health insurance policy in the United States. The case study will analyze the preliminary legislative attempts of the American Association for Labor Legislation (1912), the Wagner-Murray-Dingell Bill (1943), and Truman's support of the W-M-D Bill (1945). Continuing legislative debates of the Kerr-Mills Bill (1960), the Medicare/Medicaid Legislation (1965), and Nixon's Comprehensive Health Insurance Program of 1974 will also be analyzed. President Clinton's Health Security Act (1993) will be analyzed in detail. Results: Particular ideas about national health care problems and national health policies as they are defined and articulated through a rational public process have little substantial impact on how they are ultimately dealt with. The episodic shifts and the ebbs and flows in direction of national health insurance policy are understandable when analyzed and viewed through lens that see the impact of other realms external to the formal health policy process. Conclusions: Problem definition analysis of the intricacies and impact of various forces external to the formal health policy process on specific historical legislative debates and policy decisions about national health insurance is critical to understanding national health policy outcomes and in anticipating future proposed health policies.