to the question of causation in a specific person hinges on knowledge of the exposure received by that individual and of other factors that may be relevant. If the scientific evidence is incomplete, there may be uncertainty on the question of causation generally; if there is limited or no information on exposure of individual claimants or if other factors also contribute to disease causation, there may be uncertainty on the question of individual causation.

To provide benefits to veterans in the face of these two broad types of uncertainty, Congress and VA make presumptive decisions that bridge gaps in the evidence related to causation and to exposure. Presumptions may relieve the veteran of persuading VA that the exposure produced the adverse health outcome and of proving that an exposure occurred during military service (Pamperin, 2006). Once a medical condition is service connected through presumptions, and the veteran can document military service consistent with having received the given exposure, the veteran only has to show the basic fact that he or she suffers from the condition in order to receive a disability payment and eligibility for medical care (Zeglin, 2006).

In 2004, Congress established the Veterans’ Disability Benefits Commission (the Commission), which was charged with “studying the benefits provided to compensate and assist veterans for disabilities attributable to military service” (VDBC, 2006, p. 1; as found in Appendix A). The Commission identified the presumptive disability decision-making process as a topic needing assessment and asked the Institute of Medicine (IOM) to establish a committee for this purpose that would be funded by VA. The resulting committee, the Committee on Evaluation of the Presumptive Disability Decision-Making Process for Veterans (the Committee), was given the following charge by VA:

• Describe and evaluate the current model used to recognize diseases that are subject to service connection on a presumptive basis.

• If appropriate, propose a scientific framework that would justify recognizing or not recognizing conditions as presumptive.

The Commission further elaborated the charge, asking the Committee to “help ensure that future veterans are granted service connection under a presumptive basis based on the best scientific evidence available” (VDBC, 2006, p. 4; as found in Appendix A). The Commission asked the Committee to “evaluate the current model used to determine diseases that qualify for service connection on a presumptive basis, and if appropriate, propose improvements in the model” (VDBC, 2006, p. 1; as found in Appendix A). The Commission emphasized that “having a method of granting service connection quickly and fairly based on a presumption is