Book excerpt: Optical beams are electromagnetic waves that remain essentially concentrated around a mean axis upon free propagation or that are guided by suitable structures. The study of these beams has existed long ago and since then this field has been a focus of active investigation. However, in recent years, the interest on optical beams has further increased, due to the availability of many types of laser sources, characterized by very different properties, as far as their polarization, coherence, spectral content, and spatial distribution are concerned.This book contains lectures presented in the 35th International School of Quantum Electronics at the Ettore Majorana Centre in Erice, Sicily. It gives the latest coverage on the development and advance in “Free and Guided Optical Beams”. The purpose of these lectures was to give an updated overview, as complete as possible, on topics concerning the propagation of light beams in free space, in materials, and in guiding structures, and to provide the tools needed to its study, both from the theoretical and the application point of view.The lectures presented here are written in extended review-like format. Both introductory fundamental topics and recent research results are reviewed, making this an indispensible book for novice as well as experts in this field.The proceedings have been selected for coverage in:• Index to Scientific & Technical Proceedings® (ISTP® / ISI Proceedings)• Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings)• CC Proceedings — Engineering & Physical Sciences