be appropriate. The rationale that led to the planning of the symposium and the titles of the ses­ sions is outlined in the Introduction. We hope that this volume gathers some useful information, not only for radiation biologists, but also for colleagues en­ gaged either in fundamental cell research or in the application in the field of radiation therapy and pro­ tection. The conference would not have been possible without the generous support of the European Communities and the cosponsorship of the Deutsche Gesellschaft fUr Biophysik. If it was to a certain extent successful, then the merit goes to the very active engagement of all participants. I should like to thank my coworkers for their devoted help in the organisation, particularly Dr. Eckart Schneider, Dr. Elmar Gocke, Maria Hlawica, and Eva-Maria Peter for secretarial help.