The low viscosity of liquid helium makes it possible to construct compact wind tunnels that can sustain flows with extremely high Reynolds numbers; these would have applications ranging from basic investigations of turbulence to practical testing of supersonic aircraft. Based on papers presented at a workshop held at the University of Oregon in October of 1989, the contributions in this volume discuss both the problems of the design of such wind tunnels and the relevant properties of helium. Contributors include researchers and engineers in condensed-matter physics, fluid dynamics, mathematics, aerospace engineering, computer simulation, and cryogenics. Papers have been brought up to date, and the editor has provided a thorough introduction to the subject and a review of the current state of the art in 1991.