The"4thCologne-Bonn-ZermattSymposium:TheDenseInterstellarMedium in Galaxies" took place in Zermatt, Switzerland, from September 22nd to 26th, 2003. This symposium continued the series of conferences on the dense interstellar medium which has been organized every 5 years since 1988 by the I. Physikalisches Institut der Unversit. at .. zuKoln...Re?ecting the by now well established and fruitful collaboration between the MPI ffur ...Radioastronomie, the Radioastronomisches Institut der Universit. at .. Bonn and the I. Physikal- ches Institut der Universit. at .. zu Koln .. in the context of the Sonderforschun- bereich 494 "The Evolution of Interstellar Matter: THz-Spectroscopy in the Laboratory and in Space", the symposium is now organized jointly by these three institutes. The conference covered a wide range of topics: starting at the largest scales and earliest times in the history of the Universe, it focussed next on galaxy evolution and their structure and dynamics. New and very exciting results on the black hole in the center of the Milky Way and the violent ISM in its immediate vicinity were presented. It continued on the cosmic cycle of star formation and evolution, and reached down to the microphysical p- cesses determining the physical and chemical conditions of the interstellar matter as the important agent for this cosmic cycle.