We are requesting support to purchase a SGI Power Challenge XL 4 processor supercomputer. This computer will be used by a core group of 8 users, all with primary or joint appointments in the Department of Biomedical Engineering. Eleven projects are proposed, with nine receiving direct support from the NIH. The scope of the projects are broad, and include modeling of neural networks in the central auditory system, studies of blood flow and oxygen delivery in the microvascular bed, electrical and mechanical dynamics of cardiac networks, and measurement of strain fields in real hearts using MRI. Despite this breadth, the projects have several features in common. First, each modeling project is closely linked to the underlying biology of the system being studied; in most cases the modelers are doing the experiments on which the models are based. Second, because the models incorporate a high degree of biophysical detail, they are computationally demanding. While some of the participants in this project have access to remote supercomputing, that access is not sufficient to assure timely progress in their research. Award of this instrument will have a direct and important stimulating effect on each of these projects. It will also enhance the ability of the Department of Biomedical Engineering to play a leading international role in the development of the field of Computational Biology.