The Workshop on Hybrid Formulations of Wave Propagat~on and Scattering underwent a sequence of iterations before emerging in the format recorded here. These iterations were caused by various administrative and logistical problems which need not be detailed. However, its direction being set initially, the iterations led to modifications of the original concept so that the final form was arrived at through an indirect approach. This circumstance may ex­ plain some possible deficiencies which might have been removed, had the final concept been implemented directly. The motivation arose from a perception that the newly restored interest, coupled with new developments, in hybrid methods employ­ ing progressing wave fields and oscillatory wave fields for time­ harmonic and transient guided propagation in manmade or general geo­ physical environments, and for scattering by targets and irregulari­ ties, merits exposure to the wider scientific community. Accord­ ingly, a meeting with highly tutorial content was envisaged. For administrative reasons, related to sponsorship and organizational structure, this objective could not be realized but, eventually, there emerged the possibility of convening an Advanced Research Workshop (ARW) under the auspices of the NATO Advanced Study Insti­ tute Series. The original concept was then modified to accommodate a Workshop, wherein state-of-the-art science is discussed by a relatively small group of specialists, instead of tutorial presenta­ tions of more basic material.

I: Rays and Modes.- 1. Progressing Fields, Oscillatory Fields, and Hybrid Combinations.- 2. Transform Relations between Rays and Modes.- 3. Spectral Synthesis and Adiabatic Invariants for Non-Uniform Waveguides.- 4. Rays, Modes and Flux.- 5. Ray/Mode Trajectories and Shadows in the Horizontal Plane by Ray Invariants.- 6. Acoustic Propagation in A Wedge-Shaped Ocean with Perfectly Reflecting Boundaries.- II: Rays and Beams.- 1. A Spectral Extended Ray Method for Edge Diffraction.- 2. Modal Edge-Diffraction Coefficients for Cylindrically and Spherically Curved Concave Surfaces.- 3. Rays in Tapered Waveguides.- 4. Numerical Computation of Elastic Wavefields in Anisotropic Elastic Media in the Presence of Caustics.- 5. Complex Rays.- 6. Imaging and Propagation of Beams in Metallic or Dielectric Waveguides.- 7. Gaussian Beam Transformation through Lenses and by Curved Gratings.- 8. Gaussian Beams in Anisotropic Elastic Media and Applications.- III: Transient Propagation and Diffraction.- 1. The Singularity Expansion Representation of Surface Current on A Perfectly Conducting Scatterer.- 2. Wave front Interpretation of SEM Resonances, Turn-On Times, and Entire Functions.- 3. Non-Dispersive Approximations for Transient Ray Fields in An Inhomogeneous Medium.- 4. Time-Domain Weyl Plane-Wave Representation for Wave Functions.- IV: Numerical Modeling.- 1. Numerical Models in Underwater Acoustics.- 2. Modelling of Pulse Propagation in Layered Media Using A New Fast Field Program.- 3. Calculation of Synthetic Seismograms in Layered Media by Means of A Modified Propagator Matrix Method.- 4. The Beam Propagating Method in Integrated Optics.- 5. Time Domain Solution of Nonlinear Pulse Propagation.- 6. Stratification Methods in Waveguiding Structures.- Conclusions.- List of Participants.- Index of Subjects.