Inverse problems in wave propagation concern extraction of information about distant structural features from the measurements of scattered waves. Tasks of this nature arise in geophysics, ocean acoustics, civil and environmental engineering, ultrasonic nondestructive testing, biomedical ultrasonics, radar, astrophysics, and other areas of science and technology. The papers in this volume represent most of these scientific and technical topics, together with fundamental mathematical investigations of the relation between waves and scatterers.