Young Stellar Objects (YSO) Evolution -- Outflow, Infall, and Rotation in High-Mass Star Forming Regions -- MERLIN and Puschino Observations of H2O Masers in Outer Galactic SFR S128N -- Observing Magnetic Fields in Star-Forming Regions -- Evidence for Co-Propagation of 4765- and 1720-MHz OH Masers in Star-Forming Regions -- Magnetic Fields in Star-Forming Regions: Theoretical Aspects -- VLBI Water Maser Proper Motion Measurements in Star-Forming Regions -- High-Resolution Observations in B1-IRS: Ammonia, CCS and Water Masers -- The Kinematics, Physical Condition and Magnetic Field of the W3 IRS5 Region -- EVN Observations of H2O Masers Towards the High-Mass Young Stellar Object in AFGL 5142 -- AGN/Starburst Evolution -- Gravitationally Induced Inflow in Starbursts and AGN -- Feeding Monsters — A Study of Active Galaxies -- The QSO Hosts I Zw 1 and 3C 48: Prototypes of a Merger-Driven Quasar Evolution? -- H20 Megamasers: Accretion Disks, Jet Interaction, Outflows or Massive Star Formation? -- Probing the Obscuring Medium Around Active Nuclei Using Masers: The Case of 3C 403 -- Low-Luminosity Extra-Galactic H20 Masers -- Statistical Approach -- Monitoring Water Masers in Star-Forming Regions -- Dense Gas, Chemistry and Star Formation in Luminous Galaxies -- A Molecular Ring in the Liner NGC 5218 -- Neutral Gas in Starbursts and Active Galactic Nuclei -- CO, 13CO, and [CI] in Galaxy Centers -- Diagnostics of YSO -- Chemical Evolution of Protostars -- Model of the W3(OH) Environment Based on Data for Both Maser and “Quasi-Thermal” Methanol Lines -- Long-Term Monitoring of 6.7- and 12.2-GHZ Methanol Masers -- Ultra-Compact H II Regions -- Maser Action in Methanol Transitions -- The Methanol Maser Emission in W51 -- NGC7538 IRS1 N: Modeling a Circumstellar Maser Disk -- Diagnostics of AGN/Starbursts -- Dense Molecular Gas Around Protostars and in Galactic Nuclei: PDRs and XDRs -- Molecular Absorption in Cen A on VLBI Scales -- High-Resolution Acta Observations of the Circumnuclear Molecular Clouds of NGC 4945 -- Megamasers: Molecular Diagnostics of the Nuclear ISM -- Understanding Extragalactic Hydroxyl -- The Sub-PC Scale Accretion Disk of NGC 4258 -- OH Megamasers: Circumnuclear Gas in Starbursts -- Continuum EVN and MERLIN Observations of Ultra Luminous Infrared Galaxies -- Molecular Gas in the Abell 262 Cluster Galaxy UGC 1347 -- Dense Gas Diagnostics: Maser Excitation and Variability -- Spectral Line and Continuum Radiation Propagation in a Clumpy Medium -- A Thin Ring Model for the OH Megamaser in IIIZw35.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 bene?ted greatly from the opportunity to discuss results with the experts in a wide range of areas. Similarly, we feel con?dent 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 suf?cient room enough for off-line presentations and discussions.