This volume contains the duly-submitted invited and contributed papers presented at the Fourth International Conference on Perspectives in Hadronic Physics. The conference was held at the Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy, from May 12th to 16th, 2003, and was attended by about 100 scientists from 20 countries. This conference discussed the state-of-the-art of experimental and theoretical investigations of hadronic systems, from nucleons to nuclei and dense nuclear matter, in terms of the relevant underlying degrees of freedom. The Fourth Conference focused on those experimental and theoretical topics that have been in the last few years the object of intensive investigations. All papers appearing in the volume have been refereed and properly edited.