This volume contains eight invited papers and seventy-three contributed papers presented at the Fourth International Symposium on Gas Flow and Chemical Lasers. which was held in Stresa. Italy. from September 13 to 17. 1984. The purpose of the Symposium was to record and discuss current research developments and applications related to high power lasers. Papers were solicited from the entire spectrum of activities, includ ing basic physics, aerothermodynamics, new laser media, laser design, diagnostic techniques, laser propagation. interaction phenom ena, applications. The Symposium was an opportunity for scientists and engineers representing all these disciplines to come together to report their recent work, to exchange ideas and to provide an up-to-date account of international progress in these fields. The contributed papers were reviewed by the members of the Scientific Advisory CoEmittee. who also took responsibility for formulating the program of invited lectures. As editor I wish to express my appreciation and my gratitude to people and organizations that made this Symposium a success: the Members of the Scientific Advisory Committee, the Members of the Local Organizing Committee, the Sponsors and the Symposium Secretary. A grateful acknowledgement is expressed to Dr. M. Sandra Oggiano for assistance in the organization of the Symposium and publication of these proceedings.