Two-photon physics, i.e. photon-photon collisions in electron-positron colliders, a relatively new field in elementary particle physics, has become very popular in the last 20 years. Many experiments have been performed in this field, and the theoretical implications (in particular in quantum chromodynamics) have been studied in much detail. Nine international workshops devoted to two-photon physics have taken place between 1973 and 1992.This meeting was particularly timely, since a new generation of electron-positron colliders is presently being built or planned. These colliders will involve...