This volume brings together papers accepted for the 2004 conference in the series on Subsea Control and Data Acquisition. The event, at the Total Conference Centre, Pau, France on 10 and 11 June, was organized by the Institute of Measurement and Control, based in London, in association with the Society for Underwater Technology. The organizers acknowledge with gratitude the support of Total and FMC Energy Systems, FMC Kongsberg Subsea. The conference, building on the previous events in the series, and with the theme 'Experience and Challenges', was aimed at professionals active in subsea production systems and, in particular, engaged in the control and monitoring of such systems. The demanding challenges of long offset control and monitoring, as well as enhanced oil recovery, are addressed. Operational experience of these systems is discussed along with other topics in subsea and down hole monitoring. Attention is paid to systems reliability, and regional legislation is also considered. The Institute of Measurement and Control thanks the members of the Organizing Committee, listed elsewhere in this volume, for all their assistance in stimulating and refereeing contributions and in chairing sessions. Thanks are also due to the contributing authors and all participants for bringing high-quality discussion to the event. The Chairman of the Organizing Committee, Mr Leslie Adriaansen FInstMC, deserves particular mention for his enthusiasm, diligence, and inspiration, without which the event could not have achieved its coherence and excellent technical value.