The 11th International Ionospheric Effects Symposium (IES2005) was held at the Radisson Old Town Hotel, Alexandria, Virginia, 3–5 May 2005. The series of IES conferences, which began life as American topical events, have now been held every 3 years since 1975 and have become a tradition, representing state-of-the-art ionospheric research and applications carried out within the broader international arena.
 The sponsors of IES2005 were the Office of Naval Research (ONR), the Air Force Office of Scientific Research (AFOSR), the Federal Aviation Administration (FAA), and Union Radio Scientifique Internationale (URSI, Commissions G and H). Approximately 150 papers and posters were accepted. Topics at IES2005 included: Solar Flares and Storms; Ionospheric Radio Propagation; High-Frequency Propagation and Systems; Ionospheric Effects on Space-Based Augmentation Systems; Limb Scanning Techniques and Miscellaneous GPS Activities; Ionospheric Tomography; Ionospheric Specification, Data Assimilation, and Forecasting; C/NOFS and Scintillation; System Effects; Sounder Technology; Total Electron Content; and General Phenomena.
 This special section of Radio Science includes a selection of papers derived from the published 2005 Ionospheric Effects Symposium Proceedings, which may be obtained through the National Technical Information Service, Springfield, Virginia. It was my pleasure to serve as editor of the Proceedings of IES2005, and the associate editors were Bob McCoy and David Byers. The Proceedings is a very large volume, and it includes all contributed and invited papers, some of which are report quality and are not suitable for the Radio Science readership. Approximately 60 papers were originally selected through a screening process utilizing the IES2005 session chairpersons as the selectors. Not all potential authors accepted the offer to be included in the special issue, and others fell by the wayside. For one reason or another, the number of papers presented in this special issue was ultimately reduced to ∼40. I feel that the resultant set of papers fairly represents the full range of topics covered at IES2005.
 I would like to thank the IES Steering Committee and session chairpersons for their help in the initial screening process. They include Robert McCoy (ONR), David Byers (AFOSR), Dave Anderson (University of Colorado), Paul Bernhardt (Naval Research Laboratory), Greg Bishop (Air Force Research Laboratory), Deane Bunce (Federal Aviation Administration), William B. “Trey” Cade (Air Force Weather Agency), Ray Conkright (NOAA-NGDC), Anthea Coster (MIT Haystack Observatory), Ken Davies (NOAA, retired), Pat Doherty (Boston College), Tim Fuller-Rowell (NOAA-SEC), Jack Klobuchar (emeritus), Joe Kunches (NOAA-SEC), Leo McNamara (Boston College/AFRL), Bodo Reinisch (University of Massachusetts), James Secan (Northwest Research Associates), Kevin Scro (CISF/Air Force), Haim Soicher (U.S. Army Labs representative), and John Wang (Federal Communications Commission). Naturally, I would like to acknowledge the host of reviewers who participated in the final vetting process via GEMS and made this issue one of high quality. Finally, I would like to thank the editor of Radio Science, Tarek Habashy, for the opportunity to pull this special section together.