This special issue of Plasma Physics and Controlled Fusion contains invited and contributed papers presented at the 9th IAEA Technical Meeting on H-mode Physics and Transport Barriers. This meeting was held at the Catamaran Hotel in San Diego, California, on 24-26 September, 2003, and it was organized by General Atomics. As has been the tradition at the last four meetings of this series, the programme was sub-divided into six topics. For each topic there was an invited talk whose purpose was to give an overview of the topic, based on contributed papers presented at the meeting and on external results. These talks were followed by discussion periods, which were used for extended question and answer sessions for the invited speakers or for additional short presentations by contributing speakers. For each topic there was an associated poster session for contributed papers, of which there were about 70. The topics were:Structure and dynamics of internal transport barriersStructure and dynamics of the H-mode pedestalUnderstanding transport barriers through modellingControl of transport barriersTransport within transport barriers: theorist's view of the futureDiagnostic and analysis issues for transport barriersThe topics were focused on the physics of edge and core transport barriers. Similar to the previous meeting, held in Toki, Japan, the universality of this physics in axisymmetric and non-axisymmetric machines was featured. In addition, the physics of transport barriers in relation to burning plasma experiments was emphasized. In particular, one of the hopes and goals of the participants is that the physics of transport barriers can be used to enhance the prospects for burning plasmas. Because this meeting occurred approximately 21 years after the discovery of the H-mode in 1982, a special session was held to commemorate more than 20 years of research on transport barriers. In this session, Dr R Stambaugh and Professor K Itoh presented personal views on the implications of the discovery and memories of the early days of H-mode research. In addition, Dr F Wagner, the leader of the team that published the seminal paper announcing the discovery of the H-mode, prepared remarks that were presented by Dr Stambaugh. The discovery of the H-mode provided great hope that a fusion reactor could be developed and opened the door to the field of transport barriers, a field that was beyond the dreams of most researchers in 1982. The selection of topics and invited speakers and general organization of the scientific programme were carried out by the International Programme Committee, consisting of:S Lebedev (Ioffe, Russia)K Ida (NIFS, Japan)T Takizuka (JAERI, Japan)G Saibene (EFDA, Germany)W Suttrop (IPP, Germany)M Greenwald (MIT, USA)E Synakowski (PPPL, USA)R Groebner (GA, USA)I am very grateful to the committee members for their work and advice on the preparation of the meeting. In addition, I express deep thanks to Dr Punit Gohil, the Chair of the Local Organizing Committee, and to Lupe Cerda, the Conference Coordinator, who very ably took care of numerous details related to the organization of the meeting.