In this book we present a collection of papers around the topic of Agent Com- nication. The communication between agents has been one of the major topics of research in multi-agent systems. The current work can therefore build on a number of previous workshops, the proceedings of which have been published in earlier volumes in this series. The basis of this collection is the accepted s- missions of the workshop on Agent Communication Languages which was held in conjunction with the AAMAS conference in July 2003 in Melbourne. The workshop received 15 submissions of which 12 were selected for publication in this volume. Although the number of submissions was less than expected for an important area like Agent Communication there is no reason to worry that this area does not get enough attention from the agent community. First of all, the 12 selected papers are all of high quality. The high acceptance rate is only due to this high quality and not to the necessity to select a certain number of papers. Besides the high-quality workshop papers, we noticed that many papers on Agent Communication found their way to the main conference. We decided therefore to invite a number of authors to revise and extend their papers from this conference and to combine them with the workshop papers. We believe that the current collection comprises a very good and quite complete overview of the state of the art in this area of research and gives a good indication of the topics that are of major interest at the moment.