This volume contains nearly all the papers presented at the AMS-IMS-SIAM Joint Summer Research Conference on Biofluiddynamics, held in July 1991, at the University of Washington, Seattle. The lead paper, by Sir James Lighthill, presents a comprehensive review of external flows in biology. The other papers on external and internal flows illuminate developments in the protean field of biofluiddynamics from diverse viewpoints, reflecting the field's multidisciplinary nature. For this reason, the work should be useful to mathematicians, biologists, engineers, physiologists, cardiologists and oceanographers alike. The papers highlight a number of problems that have remained largely unexplored due to the difficulty of addressing biological flow motions, which are often governed by large systems of nonlinear differential equations and involve complex geometries. However, recent advances in computational fluid dynamics have expanded opportunities to solve such problems. These developments have increased interest in areas such as the mechanisms of blood and air flow in humans, the dynamic ecology of the oceans, animal swimming and flight, to name a few.