In the editorial of the September issue of this year it wasannounced that a number of special issues of Nuclear Fusion will be published which will address subjects for which the integration of physics and enabling technology is essential. This November issue is dedicated to Electron Cyclotron Wave (ECW) physics and technology.This issue is a compilation of 25 papers which form a snapshot of what is currently going on in the research area of ECW physics and technology for fusion devices. The collected articles are mostly derived from conference contributions (EC-12, SMP-2002, IAEA Lyon conference), rewritten and extended for the purpose of this special issue and submitted to our standard double-referee peer review. Several regular submissions, not related to conference contributions, are also included. This compilation is somewhat arbitrary as the editor is dependent on incoming submissions. It was decided not to delay publication of the specialized subject-relatedpapers by commissioning introductory review articles, which would be subject to longer lead-times. Also, a number of regular papers, whose subject would have fitted perfectly in this issue, were published earlier in the year (see below). The 25 articles are arranged in a sequence from theory, via experiments on heating and current-drive, electron heat-transport studies, application of ECW emission measurements, to ECW sources (gyrotrons), transmission-lines, microwave technology, with one article on an application outside fusion research. One article was submitted as a Letter (Cappa and Castejon) but it has been placed logically within the sequence. I hope that this special issue will give the interested reader a state-of-the-art picture of the field of ECW physics and technology in nuclear fusion research and be of help for specialists working in the field.The following articles, which are closely related to the subject of this special issue, were published in earlier issues this year:A. Manini, J.-M. Moret, F. Ryter and the ASDEX Upgrade Team 2003Signal processing techniques based on singular value decomposition applied to modulated ECH experiments Nucl. Fusion43 490--511C. Angioni, T.P. Goodman, M.A. Henderson and O. Sauter 2003Effects of localized electron heating and current drive on the sawtooth period Nucl. Fusion43 455--468V. Pericoli Ridolfini et al 2003Progress towards internal transport barriers at high plasma density sustained by pure electron heating and current drive in the FTU tokamak Nucl. Fusion43 469--478K. Sakamoto et al 2003Development of 170 and 110 GHz gyrotrons for fusion devices Nucl. Fusion43 729--737C.C. Petty et al 2003Effects of electron trapping and transport on electron cyclotron current drive on DIII--D Nucl. Fusion43 700--707F. Leuterer, K. Kirov, G. Pereverzev, F. Ryter and D. Wagner 2003Modulated ECRH power deposition in ASDEX Upgrade Nucl. Fusion43 744--748R. Prater et al 2003Discharge improvement through control of neoclassical tearing modes by localized ECCD in DIII-D Nucl. Fusion43 1128--1134K. Nagasaki, A. Isayama, S. Ide and JT-60 team 2003Stabilization effect of early ECCD on a neoclassical tearing mode in the JT-60U tokamak Nucl. Fusion43 L7--L10