Animals have been used as models for humans at the NIH for over 100 years. Their continued use was the subject of the NIH Conference, "Modeling in Biomedical Research: An Assessment of Current and Potential Approaches, Applications to Studies in Cardiovascular/Pulmonary Function and Diabetes." [reference: same title, May 1-3, 1989] The motivating hypothesis for the conference was that continued innovation and development in model systems is important to progress in improving the health of the Nation.