The European Workshop on Astronomical Molecules was held at ‘The Conference Building’ in Zwolle, the Netherlands, on 18–20 February 2004. The idea behind the workshop was to bring together astronomers studying similar processes in different astrophysical environments; masers and dense molecular gas around young stars and galactic nuclei. There is considerable overlap in physical and chemical phenomena between these environments, with scales ranging from circumstellar to central regions of galaxies. The workshop became a meeting place of observers and theorists as well as young and senior astronomers. The venue of the meeting facilitated continuous stimulated discussions in a relaxed atmosphere throughout the meeting and after sessions in the hotspots of the cosy town of Zwolle. This issue includes 12 reviews and 27 contributed papers presented in this Wo- shop, all of them were refereed by invited speakers or the editors. The quality of the papers is outstanding. The projects discussed here are often in an early stage and undoubtedly their progress has benefited greatly from the opportunity to discuss results with the experts in a wide range of areas. Similarly, we feel confident that the interaction of specialists with different backgrounds will initiate many new projects and collaborations. The format of the meeting was special since all participants were given the opportunity to make an oral presentation and there were no posters. In addition, the schedule allowed sufficient room enough for off-line presentations and discussions.