During the past decade, the advent of sophisticated numerical techniques has led to the publication of a great number of papers on scattering and diffraction containing a wealth of data, often displayed in very attractive fashion such as multicolor and three-dimensional graphs. However, many of these contributions are deficient in providing physical insights on the results obtained. Such insights can only be gained through analytical solutions that offer the added advantage of providing validation tools for computer codes.
 This special section of Radio Science is devoted to recent and original contributions to analytical methods in direct and inverse scattering and diffraction. Although the primary emphasis is on electromagnetic waves, several results are also applicable to acoustic or elastic boundary-value problems. The issue consists of 35 papers devoted to such diverse topics as scattering by conducting, impedance, and penetrable wedges; circular and elliptic cones; spherical, cylindrical, and paraboloidal structures made of metamaterials; cavities filled with isorefractive material; photonic band-gap structures. It contains studies on Wiener-Hopf factorization; on backscattering by rough surfaces and random media; on excitation of random cables; on scattering of ELF waves by underground formations; on propagation along planar discontinuities, periodic arrays, and metamaterial nanocomponents; on diffraction by grated dielectric slabs; on refinements of high-frequency methods; on reconstruction of complex permittivity in a waveguide; on advances in regularization techniques for scattering and diffraction; on radiation from prolate spheroidal antennas and large arrays. With the exception of a contribution (RS4006) that was inadvertently published early in issue 4 of volume 42, all papers intended for the special section appear in this issue of Radio Science. Several contributions are seminal works that fundamentally advance our understanding of scattering and diffraction phenomena.
 I am grateful to all the Authors who accepted my invitation to contribute to the special section, and to the staff of Radio Science for their expert support in the preparation of the issue: Tarek Habashy who, as Editor-in-Chief, approved the issue and encouraged its production; Pam Calliham, Barbara Hunt, Jane Seebold, Rick Wooten, Shawna Bird, and all others who assisted and prodded me into bringing this important project to successful conclusion.